diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/BatchedRemoteIterator.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/BatchedRemoteIterator.java
new file mode 100644
index 0000000..607fffb
--- /dev/null
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/BatchedRemoteIterator.java
@@ -0,0 +1,118 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.fs;
+
+import java.io.IOException;
+import java.util.List;
+import java.util.NoSuchElementException;
+
+/**
+ * A RemoteIterator that fetches elements in batches.
+ */
+public abstract class BatchedRemoteIterator<K, E> implements RemoteIterator<E> {
+  public interface BatchedEntries<E> {
+    public E get(int i);
+    public int size();
+    public boolean hasMore();
+  }
+
+  public static class BatchedListEntries<E> implements BatchedEntries<E> {
+    private final List<E> entries;
+    private final boolean hasMore;
+
+    public BatchedListEntries(List<E> entries, boolean hasMore) {
+      this.entries = entries;
+      this.hasMore = hasMore;
+    }
+
+    public E get(int i) {
+      return entries.get(i);
+    }
+
+    public int size() {
+      return entries.size();
+    }
+
+    public boolean hasMore() {
+      return hasMore;
+    }
+  }
+
+  private K prevKey;
+  private BatchedEntries<E> entries;
+  private int idx;
+
+  public BatchedRemoteIterator(K prevKey) {
+    this.prevKey = prevKey;
+    this.entries = null;
+    this.idx = -1;
+  }
+
+  /**
+   * Perform the actual remote request.
+   * 
+   * @param prevKey The key to send.
+   * @return A list of replies.
+   */
+  public abstract BatchedEntries<E> makeRequest(K prevKey) throws IOException;
+
+  private void makeRequest() throws IOException {
+    idx = 0;
+    entries = null;
+    entries = makeRequest(prevKey);
+    if (entries.size() == 0) {
+      entries = null;
+    }
+  }
+
+  private void makeRequestIfNeeded() throws IOException {
+    if (idx == -1) {
+      makeRequest();
+    } else if ((entries != null) && (idx >= entries.size())) {
+      if (!entries.hasMore()) {
+        // Last time, we got fewer entries than requested.
+        // So we should be at the end.
+        entries = null;
+      } else {
+        makeRequest();
+      }
+    }
+  }
+
+  @Override
+  public boolean hasNext() throws IOException {
+    makeRequestIfNeeded();
+    return (entries != null);
+  }
+
+  /**
+   * Return the next list key associated with an element.
+   */
+  public abstract K elementToPrevKey(E element);
+
+  @Override
+  public E next() throws IOException {
+    makeRequestIfNeeded();
+    if (entries == null) {
+      throw new NoSuchElementException();
+    }
+    E entry = entries.get(idx++);
+    prevKey = elementToPrevKey(entry);
+    return entry;
+  }
+}
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/permission/FsPermission.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/permission/FsPermission.java
index 3db9acb..9a5d916 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/permission/FsPermission.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/permission/FsPermission.java
@@ -304,6 +304,13 @@
   }
 
   /**
+   * Get the default permission for cache pools.
+   */
+  public static FsPermission getCachePoolDefault() {
+    return new FsPermission((short)00755);
+  }
+
+  /**
    * Create a FsPermission from a Unix symbolic permission string
    * @param unixSymbolicPermission e.g. "-rw-rw-rw-"
    */
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/Text.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/Text.java
index a5c8b1e..e4490f1 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/Text.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/Text.java
@@ -454,10 +454,7 @@
   /** Read a UTF8 encoded string from in
    */
   public static String readString(DataInput in) throws IOException {
-    int length = WritableUtils.readVInt(in);
-    byte [] bytes = new byte[length];
-    in.readFully(bytes, 0, length);
-    return decode(bytes);
+    return readString(in, Integer.MAX_VALUE);
   }
   
   /** Read a UTF8 encoded string with a maximum size
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/nativeio/NativeIO.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/nativeio/NativeIO.java
index 1412d61..3d6ce7b 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/nativeio/NativeIO.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/nativeio/NativeIO.java
@@ -23,6 +23,7 @@
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.RandomAccessFile;
+import java.nio.ByteBuffer;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 
@@ -145,6 +146,12 @@
       return NativeCodeLoader.isNativeCodeLoaded() && nativeLoaded;
     }
 
+    private static void assertCodeLoaded() throws IOException {
+      if (!isAvailable()) {
+        throw new IOException("NativeIO was not loaded");
+      }
+    }
+
     /** Wrapper around open(2) */
     public static native FileDescriptor open(String path, int flags, int mode) throws IOException;
     /** Wrapper around fstat(2) */
@@ -225,6 +232,46 @@
       }
     }
 
+    static native void mlock_native(
+        ByteBuffer buffer, long len) throws NativeIOException;
+    static native void munlock_native(
+        ByteBuffer buffer, long len) throws NativeIOException;
+
+    /**
+     * Locks the provided direct ByteBuffer into memory, preventing it from
+     * swapping out. After a buffer is locked, future accesses will not incur
+     * a page fault.
+     * 
+     * See the mlock(2) man page for more information.
+     * 
+     * @throws NativeIOException
+     */
+    public static void mlock(ByteBuffer buffer, long len)
+        throws IOException {
+      assertCodeLoaded();
+      if (!buffer.isDirect()) {
+        throw new IOException("Cannot mlock a non-direct ByteBuffer");
+      }
+      mlock_native(buffer, len);
+    }
+
+    /**
+     * Unlocks a locked direct ByteBuffer, allowing it to swap out of memory.
+     * This is a no-op if the ByteBuffer was not previously locked.
+     * 
+     * See the munlock(2) man page for more information.
+     * 
+     * @throws NativeIOException
+     */
+    public static void munlock(ByteBuffer buffer, long len)
+        throws IOException {
+      assertCodeLoaded();
+      if (!buffer.isDirect()) {
+        throw new IOException("Cannot munlock a non-direct ByteBuffer");
+      }
+      munlock_native(buffer, len);
+    }
+
     /** Linux only methods used for getOwner() implementation */
     private static native long getUIDforFDOwnerforOwner(FileDescriptor fd) throws IOException;
     private static native String getUserName(long uid) throws IOException;
@@ -478,6 +525,20 @@
   /** Initialize the JNI method ID and class ID cache */
   private static native void initNative();
 
+  /**
+   * Get the maximum number of bytes that can be locked into memory at any
+   * given point.
+   *
+   * @return 0 if no bytes can be locked into memory;
+   *         Long.MAX_VALUE if there is no limit;
+   *         The number of bytes that can be locked into memory otherwise.
+   */
+  public static long getMemlockLimit() {
+    return isAvailable() ? getMemlockLimit0() : 0;
+  }
+
+  private static native long getMemlockLimit0();
+  
   private static class CachedUid {
     final long timestamp;
     final String username;
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/UserGroupInformation.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/UserGroupInformation.java
index 3bb8073..5f82250 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/UserGroupInformation.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/UserGroupInformation.java
@@ -1254,6 +1254,14 @@
     return null;
   }
 
+  public String getPrimaryGroupName() throws IOException {
+    String[] groups = getGroupNames();
+    if (groups.length == 0) {
+      throw new IOException("There is no primary group for UGI " + this);
+    }
+    return groups[0];
+  }
+
   /**
    * Get the user's full principal name.
    * @return the user's full principal name.
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/IntrusiveCollection.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/IntrusiveCollection.java
new file mode 100644
index 0000000..0512d4a
--- /dev/null
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/IntrusiveCollection.java
@@ -0,0 +1,373 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.util;
+
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.classification.InterfaceAudience;
+
+import com.google.common.base.Preconditions;
+
+/**
+ * Implements an intrusive doubly-linked list.
+ *
+ * An intrusive linked list is one in which the elements themselves are
+ * responsible for storing the pointers to previous and next elements.
+ * This can save a lot of memory if there are many elements in the list or
+ * many lists.
+ */
+@InterfaceAudience.Private
+public class IntrusiveCollection<E extends IntrusiveCollection.Element>
+    implements Collection<E> {
+  /**
+   * An element contained in this list.
+   *
+   * We pass the list itself as a parameter so that elements can belong to
+   * multiple lists.  (The element will need to store separate prev and next
+   * pointers for each.)
+   */
+  @InterfaceAudience.Private
+  public interface Element {
+    /**
+     * Insert this element into the list.  This is the first thing that will
+     * be called on the element.
+     */
+    void insertInternal(IntrusiveCollection<? extends Element> list,
+        Element prev, Element next);
+
+    /**
+     * Set the prev pointer of an element already in the list.
+     */
+    void setPrev(IntrusiveCollection<? extends Element> list, Element prev);
+
+    /**
+     * Set the next pointer of an element already in the list.
+     */
+    void setNext(IntrusiveCollection<? extends Element> list, Element next);
+
+    /**
+     * Remove an element from the list.  This is the last thing that will be
+     * called on an element.
+     */
+    void removeInternal(IntrusiveCollection<? extends Element> list);
+
+    /**
+     * Get the prev pointer of an element.
+     */
+    Element getPrev(IntrusiveCollection<? extends Element> list);
+
+    /**
+     * Get the next pointer of an element.
+     */
+    Element getNext(IntrusiveCollection<? extends Element> list);
+
+    /**
+     * Returns true if this element is in the provided list.
+     */
+    boolean isInList(IntrusiveCollection<? extends Element> list);
+  }
+
+  private Element root = new Element() {
+    // We keep references to the first and last elements for easy access.
+    Element first = this;
+    Element last = this;
+  
+    @Override
+    public void insertInternal(IntrusiveCollection<? extends Element> list,
+        Element prev, Element next) {
+      throw new RuntimeException("Can't insert root element");
+    }
+
+    @Override
+    public void setPrev(IntrusiveCollection<? extends Element> list,
+        Element prev) {
+      Preconditions.checkState(list == IntrusiveCollection.this);
+      last = prev;
+    }
+
+    @Override
+    public void setNext(IntrusiveCollection<? extends Element> list,
+        Element next) {
+      Preconditions.checkState(list == IntrusiveCollection.this);
+      first = next;
+    }
+  
+    @Override
+    public void removeInternal(IntrusiveCollection<? extends Element> list) {
+      throw new RuntimeException("Can't remove root element");
+    }
+    
+    @Override
+    public Element getNext(
+        IntrusiveCollection<? extends Element> list) {
+      Preconditions.checkState(list == IntrusiveCollection.this);
+      return first;
+    }
+  
+    @Override
+    public Element getPrev(
+        IntrusiveCollection<? extends Element> list) {
+      Preconditions.checkState(list == IntrusiveCollection.this);
+      return last;
+    }
+
+    @Override
+    public boolean isInList(IntrusiveCollection<? extends Element> list) {
+      return list == IntrusiveCollection.this;
+    }
+
+    @Override
+    public String toString() {
+      return "root"; // + IntrusiveCollection.this + "]";
+    }
+  };
+
+  private int size = 0;
+
+  /**
+   * An iterator over the intrusive collection.
+   *
+   * Currently, you can remove elements from the list using
+   * #{IntrusiveIterator#remove()}, but modifying the collection in other
+   * ways during the iteration is not supported.
+   */
+  public class IntrusiveIterator implements Iterator<E> {
+    Element cur;
+    Element next;
+
+    IntrusiveIterator() {
+      this.cur = root;
+      this.next = null;
+    }
+
+    @Override
+    public boolean hasNext() {
+      if (next == null) {
+        next = cur.getNext(IntrusiveCollection.this);
+      }
+      return next != root;
+    }
+
+    @SuppressWarnings("unchecked")
+    @Override
+    public E next() {
+      if (next == null) {
+        next = cur.getNext(IntrusiveCollection.this);
+      }
+      if (next == root) {
+        throw new NoSuchElementException();
+      }
+      cur = next;
+      next = null;
+      return (E)cur;
+    }
+
+    @Override
+    public void remove() {
+      if (cur == null) {
+        throw new IllegalStateException("Already called remove " +
+            "once on this element.");
+      }
+      next = removeElement(cur);
+      cur = null;
+    }
+  }
+  
+  private Element removeElement(Element elem) {
+    Element prev = elem.getPrev(IntrusiveCollection.this);
+    Element next = elem.getNext(IntrusiveCollection.this);
+    elem.removeInternal(IntrusiveCollection.this);
+    prev.setNext(IntrusiveCollection.this, next);
+    next.setPrev(IntrusiveCollection.this, prev);
+    size--;
+    return next;
+  }
+
+  /**
+   * Get an iterator over the list.  This can be used to remove elements.
+   * It is not safe to do concurrent modifications from other threads while
+   * using this iterator.
+   * 
+   * @return         The iterator.
+   */
+  public Iterator<E> iterator() {
+    return new IntrusiveIterator();
+  }
+
+  @Override
+  public int size() {
+    return size;
+  }
+
+  @Override
+  public boolean isEmpty() {
+    return size == 0;
+  }
+
+  @Override
+  public boolean contains(Object o) {
+    try {
+      Element element = (Element)o;
+      return element.isInList(this);
+    } catch (ClassCastException e) {
+      return false;
+    }
+  }
+
+  @Override
+  public Object[] toArray() {
+    Object ret[] = new Object[size];
+    int i = 0;
+    for (Iterator<E> iter = iterator(); iter.hasNext(); ) {
+      ret[i++] = iter.next();
+    }
+    return ret;
+  }
+
+  @SuppressWarnings("unchecked")
+  @Override
+  public <T> T[] toArray(T[] array) {
+    if (array.length < size) {
+      return (T[])toArray();
+    } else {
+      int i = 0;
+      for (Iterator<E> iter = iterator(); iter.hasNext(); ) {
+        array[i++] = (T)iter.next();
+      }
+    }
+    return array;
+  }
+
+  /**
+   * Add an element to the end of the list.
+   * 
+   * @param elem     The new element to add.
+   */
+  @Override
+  public boolean add(E elem) {
+    if (elem == null) {
+      return false;
+    }
+    if (elem.isInList(this)) {
+      return false;
+    }
+    Element prev = root.getPrev(IntrusiveCollection.this);
+    prev.setNext(IntrusiveCollection.this, elem);
+    root.setPrev(IntrusiveCollection.this, elem);
+    elem.insertInternal(IntrusiveCollection.this, prev, root);
+    size++;
+    return true;
+  }
+
+  /**
+   * Add an element to the front of the list.
+   *
+   * @param elem     The new element to add.
+   */
+  public boolean addFirst(Element elem) {
+    if (elem == null) {
+      return false;
+    }
+    if (elem.isInList(this)) {
+      return false;
+    }
+    Element next = root.getNext(IntrusiveCollection.this);
+    next.setPrev(IntrusiveCollection.this, elem);
+    root.setNext(IntrusiveCollection.this, elem);
+    elem.insertInternal(IntrusiveCollection.this, root, next);
+    size++;
+    return true;
+  }
+
+  public static final Log LOG = LogFactory.getLog(IntrusiveCollection.class);
+
+  @Override
+  public boolean remove(Object o) {
+    try {
+      Element elem = (Element)o;
+      if (!elem.isInList(this)) {
+        return false;
+      }
+      removeElement(elem);
+      return true;
+    } catch (ClassCastException e) {
+      return false;
+    }
+  }
+
+  @Override
+  public boolean containsAll(Collection<?> collection) {
+    for (Object o : collection) {
+      if (!contains(o)) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  @Override
+  public boolean addAll(Collection<? extends E> collection) {
+    boolean changed = false;
+    for (E elem : collection) {
+      if (add(elem)) {
+        changed = true;
+      }
+    }
+    return changed;
+  }
+
+  @Override
+  public boolean removeAll(Collection<?> collection) {
+    boolean changed = false;
+    for (Object elem : collection) {
+      if (remove(elem)) {
+        changed = true;
+      }
+    }
+    return changed;
+  }
+
+  @Override
+  public boolean retainAll(Collection<?> collection) {
+    boolean changed = false;
+    for (Iterator<E> iter = iterator();
+        iter.hasNext(); ) {
+      Element elem = iter.next();
+      if (!collection.contains(elem)) {
+        iter.remove();
+        changed = true;
+      }
+    }
+    return changed;
+  }
+
+  /**
+   * Remove all elements.
+   */
+  @Override
+  public void clear() {
+    for (Iterator<E> iter = iterator(); iter.hasNext(); ) {
+      iter.next();
+      iter.remove();
+    }
+  }
+}
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/LightWeightCache.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/LightWeightCache.java
index 7e7ad2c..a0a553a 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/LightWeightCache.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/LightWeightCache.java
@@ -18,6 +18,7 @@
 package org.apache.hadoop.util;
 
 import java.util.Comparator;
+import java.util.Iterator;
 import java.util.PriorityQueue;
 
 import org.apache.hadoop.HadoopIllegalArgumentException;
@@ -235,4 +236,28 @@
     }
     return removed;
   }
+
+  @Override
+  public Iterator<E> iterator() {
+    final Iterator<E> iter = super.iterator();
+    return new Iterator<E>() {
+      @Override
+      public boolean hasNext() {
+        return iter.hasNext();
+      }
+
+      @Override
+      public E next() {
+        return iter.next();
+      }
+
+      @Override
+      public void remove() {
+        // It would be tricky to support this because LightWeightCache#remove
+        // may evict multiple elements via evictExpiredEntries.
+        throw new UnsupportedOperationException("Remove via iterator is " +
+            "not supported for LightWeightCache");
+      }
+    };
+  }
 }
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/LightWeightGSet.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/LightWeightGSet.java
index 7686069..50e291d 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/LightWeightGSet.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/LightWeightGSet.java
@@ -246,10 +246,10 @@
 
   private class SetIterator implements Iterator<E> {
     /** The starting modification for fail-fast. */
-    private final int startModification = modification;
+    private int iterModification = modification;
     /** The current index of the entry array. */
     private int index = -1;
-    /** The next element to return. */
+    private LinkedElement cur = null;
     private LinkedElement next = nextNonemptyEntry();
 
     /** Find the next nonempty entry starting at (index + 1). */
@@ -258,30 +258,51 @@
       return index < entries.length? entries[index]: null;
     }
 
+    private void ensureNext() {
+      if (modification != iterModification) {
+        throw new ConcurrentModificationException("modification=" + modification
+            + " != iterModification = " + iterModification);
+      }
+      if (next != null) {
+        return;
+      }
+      if (cur == null) {
+        return;
+      }
+      next = cur.getNext();
+      if (next == null) {
+        next = nextNonemptyEntry();
+      }
+    }
+
     @Override
     public boolean hasNext() {
+      ensureNext();
       return next != null;
     }
 
     @Override
     public E next() {
-      if (modification != startModification) {
-        throw new ConcurrentModificationException("modification=" + modification
-            + " != startModification = " + startModification);
+      ensureNext();
+      if (next == null) {
+        throw new IllegalStateException("There are no more elements");
       }
-
-      final E e = convert(next);
-
-      //find the next element
-      final LinkedElement n = next.getNext();
-      next = n != null? n: nextNonemptyEntry();
-
-      return e;
+      cur = next;
+      next = null;
+      return convert(cur);
     }
 
+    @SuppressWarnings("unchecked")
     @Override
     public void remove() {
-      throw new UnsupportedOperationException("Remove is not supported.");
+      ensureNext();
+      if (cur == null) {
+        throw new IllegalStateException("There is no current element " +
+            "to remove");
+      }
+      LightWeightGSet.this.remove((K)cur);
+      iterModification++;
+      cur = null;
     }
   }
   
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/StringUtils.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/StringUtils.java
index 284a042..32e5572 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/StringUtils.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/StringUtils.java
@@ -905,4 +905,81 @@
     }
     return str.toString();
   }
+
+  /**
+   * From a list of command-line arguments, remove both an option and the 
+   * next argument.
+   *
+   * @param name  Name of the option to remove.  Example: -foo.
+   * @param args  List of arguments.
+   * @return      null if the option was not found; the value of the 
+   *              option otherwise.
+   */
+  public static String popOptionWithArgument(String name, List<String> args) {
+    String val = null;
+    for (Iterator<String> iter = args.iterator(); iter.hasNext(); ) {
+      String cur = iter.next();
+      if (cur.equals("--")) {
+        // stop parsing arguments when you see --
+        break;
+      } else if (cur.equals(name)) {
+        iter.remove();
+        if (!iter.hasNext()) {
+          throw new RuntimeException("option " + name + " requires 1 " +
+              "argument.");
+        }
+        val = iter.next();
+        iter.remove();
+        break;
+      }
+    }
+    return val;
+  }
+  
+  /**
+   * From a list of command-line arguments, remove an option.
+   *
+   * @param name  Name of the option to remove.  Example: -foo.
+   * @param args  List of arguments.
+   * @return      true if the option was found and removed; false otherwise.
+   */
+  public static boolean popOption(String name, List<String> args) {
+    for (Iterator<String> iter = args.iterator(); iter.hasNext(); ) {
+      String cur = iter.next();
+      if (cur.equals("--")) {
+        // stop parsing arguments when you see --
+        break;
+      } else if (cur.equals(name)) {
+        iter.remove();
+        return true;
+      }
+    }
+    return false;
+  }
+  
+  /**
+   * From a list of command-line arguments, return the first non-option
+   * argument.  Non-option arguments are those which either come after 
+   * a double dash (--) or do not start with a dash.
+   *
+   * @param args  List of arguments.
+   * @return      The first non-option argument, or null if there were none.
+   */
+  public static String popFirstNonOption(List<String> args) {
+    for (Iterator<String> iter = args.iterator(); iter.hasNext(); ) {
+      String cur = iter.next();
+      if (cur.equals("--")) {
+        if (!iter.hasNext()) {
+          return null;
+        }
+        cur = iter.next();
+        iter.remove();
+        return cur;
+      } else if (!cur.startsWith("-")) {
+        iter.remove();
+        return cur;
+      }
+    }
+    return null;
+  }
 }
diff --git a/hadoop-common-project/hadoop-common/src/main/native/src/org/apache/hadoop/io/nativeio/NativeIO.c b/hadoop-common-project/hadoop-common/src/main/native/src/org/apache/hadoop/io/nativeio/NativeIO.c
index cb21a7b..a26bf34 100644
--- a/hadoop-common-project/hadoop-common/src/main/native/src/org/apache/hadoop/io/nativeio/NativeIO.c
+++ b/hadoop-common-project/hadoop-common/src/main/native/src/org/apache/hadoop/io/nativeio/NativeIO.c
@@ -16,8 +16,6 @@
  * limitations under the License.
  */
 
-#define _GNU_SOURCE
-
 #include "org_apache_hadoop.h"
 #include "org_apache_hadoop_io_nativeio_NativeIO.h"
 
@@ -28,11 +26,15 @@
 #include <grp.h>
 #include <jni.h>
 #include <pwd.h>
+#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/mman.h>
+#include <sys/resource.h>
 #include <sys/stat.h>
 #include <sys/syscall.h>
+#include <sys/time.h>
 #include <sys/types.h>
 #include <unistd.h>
 #include "config.h"
@@ -360,6 +362,71 @@
 #endif
 }
 
+#define CHECK_DIRECT_BUFFER_ADDRESS(buf) \
+  { \
+    if (!buf) { \
+      THROW(env, "java/lang/UnsupportedOperationException", \
+        "JNI access to direct buffers not available"); \
+      return; \
+    } \
+  }
+
+/**
+ * public static native void mlock_native(
+ *   ByteBuffer buffer, long offset);
+ *
+ * The "00024" in the function name is an artifact of how JNI encodes
+ * special characters. U+0024 is '$'.
+ */
+JNIEXPORT void JNICALL
+Java_org_apache_hadoop_io_nativeio_NativeIO_00024POSIX_mlock_1native(
+  JNIEnv *env, jclass clazz,
+  jobject buffer, jlong len)
+{
+#ifdef UNIX
+  void* buf = (void*)(*env)->GetDirectBufferAddress(env, buffer);
+  PASS_EXCEPTIONS(env);
+
+  if (mlock(buf, len)) {
+    CHECK_DIRECT_BUFFER_ADDRESS(buf);
+    throw_ioe(env, errno);
+  }
+#endif
+
+#ifdef WINDOWS
+  THROW(env, "java/io/IOException",
+    "The function POSIX.mlock_native() is not supported on Windows");
+#endif
+}
+
+/**
+ * public static native void munlock_native(
+ *   ByteBuffer buffer, long offset);
+ *
+ * The "00024" in the function name is an artifact of how JNI encodes
+ * special characters. U+0024 is '$'.
+ */
+JNIEXPORT void JNICALL
+Java_org_apache_hadoop_io_nativeio_NativeIO_00024POSIX_munlock_1native(
+  JNIEnv *env, jclass clazz,
+  jobject buffer, jlong len)
+{
+#ifdef UNIX
+  void* buf = (void*)(*env)->GetDirectBufferAddress(env, buffer);
+  PASS_EXCEPTIONS(env);
+
+  if (munlock(buf, len)) {
+    CHECK_DIRECT_BUFFER_ADDRESS(buf);
+    throw_ioe(env, errno);
+  }
+#endif
+
+#ifdef WINDOWS
+  THROW(env, "java/io/IOException",
+    "The function POSIX.munlock_native() is not supported on Windows");
+#endif
+}
+
 #ifdef __FreeBSD__
 static int toFreeBSDFlags(int flags)
 {
@@ -924,6 +991,24 @@
 #endif
 }
 
+JNIEXPORT jlong JNICALL
+Java_org_apache_hadoop_io_nativeio_NativeIO_getMemlockLimit0(
+JNIEnv *env, jclass clazz)
+{
+#ifdef WINDOWS
+  return 0;
+#else
+  struct rlimit rlim;
+  int rc = getrlimit(RLIMIT_MEMLOCK, &rlim);
+  if (rc != 0) {
+    throw_ioe(env, errno);
+    return 0;
+  }
+  return (rlim.rlim_cur == RLIM_INFINITY) ?
+    INT64_MAX : rlim.rlim_cur;
+#endif
+}
+
 /**
  * vim: sw=2: ts=2: et:
  */
diff --git a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/nativeio/TestNativeIO.java b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/nativeio/TestNativeIO.java
index 2e7c62c..521ec09 100644
--- a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/nativeio/TestNativeIO.java
+++ b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/nativeio/TestNativeIO.java
@@ -24,6 +24,9 @@
 import java.io.FileReader;
 import java.io.FileWriter;
 import java.io.IOException;
+import java.nio.MappedByteBuffer;
+import java.nio.channels.FileChannel;
+import java.nio.channels.FileChannel.MapMode;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -32,6 +35,7 @@
 import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
+
 import static org.junit.Assume.*;
 import static org.junit.Assert.*;
 
@@ -45,6 +49,7 @@
 import org.apache.hadoop.fs.permission.FsPermission;
 import org.apache.hadoop.security.UserGroupInformation;
 import org.apache.hadoop.util.NativeCodeLoader;
+import org.apache.hadoop.util.Shell;
 import org.apache.hadoop.util.Time;
 
 public class TestNativeIO {
@@ -563,4 +568,60 @@
 
     FileUtils.deleteQuietly(TEST_DIR);
   }
+
+  @Test(timeout=10000)
+  public void testMlock() throws Exception {
+    assumeTrue(NativeIO.isAvailable());
+    assumeTrue(Shell.LINUX);
+    final File TEST_FILE = new File(new File(
+        System.getProperty("test.build.data","build/test/data")),
+        "testMlockFile");
+    final int BUF_LEN = 12289;
+    byte buf[] = new byte[BUF_LEN];
+    int bufSum = 0;
+    for (int i = 0; i < buf.length; i++) {
+      buf[i] = (byte)(i % 60);
+      bufSum += buf[i];
+    }
+    FileOutputStream fos = new FileOutputStream(TEST_FILE);
+    try {
+      fos.write(buf);
+      fos.getChannel().force(true);
+    } finally {
+      fos.close();
+    }
+    
+    FileInputStream fis = null;
+    FileChannel channel = null;
+    try {
+      // Map file into memory
+      fis = new FileInputStream(TEST_FILE);
+      channel = fis.getChannel();
+      long fileSize = channel.size();
+      MappedByteBuffer mapbuf = channel.map(MapMode.READ_ONLY, 0, fileSize);
+      // mlock the buffer
+      NativeIO.POSIX.mlock(mapbuf, fileSize);
+      // Read the buffer
+      int sum = 0;
+      for (int i=0; i<fileSize; i++) {
+        sum += mapbuf.get(i);
+      }
+      assertEquals("Expected sums to be equal", bufSum, sum);
+      // munlock the buffer
+      NativeIO.POSIX.munlock(mapbuf, fileSize);
+    } finally {
+      if (channel != null) {
+        channel.close();
+      }
+      if (fis != null) {
+        fis.close();
+      }
+    }
+  }
+
+  @Test(timeout=10000)
+  public void testGetMemlockLimit() throws Exception {
+    assumeTrue(NativeIO.isAvailable());
+    NativeIO.getMemlockLimit();
+  }
 }
diff --git a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/util/TestLightWeightGSet.java b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/util/TestLightWeightGSet.java
new file mode 100644
index 0000000..671dd37
--- /dev/null
+++ b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/util/TestLightWeightGSet.java
@@ -0,0 +1,110 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.util;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.Random;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.util.LightWeightGSet.LinkedElement;
+import org.junit.Assert;
+import org.junit.Test;
+
+/** Testing {@link LightWeightGSet} */
+public class TestLightWeightGSet {
+  public static final Log LOG = LogFactory.getLog(TestLightWeightGSet.class);
+
+  private static ArrayList<Integer> getRandomList(int length, int randomSeed) {
+    Random random = new Random(randomSeed);
+    ArrayList<Integer> list = new ArrayList<Integer>(length);
+    for (int i = 0; i < length; i++) {
+      list.add(random.nextInt());
+    }
+    return list;
+  }
+  
+  private static class TestElement implements LightWeightGSet.LinkedElement {
+    private final int val;
+    private LinkedElement next;
+
+    TestElement(int val) {
+      this.val = val;
+      this.next = null;
+    }
+    
+    public int getVal() {
+      return val;
+    }
+
+    @Override
+    public void setNext(LinkedElement next) {
+      this.next = next;
+    }
+
+    @Override
+    public LinkedElement getNext() {
+      return next;
+    }
+  }
+
+  @Test(timeout=60000)
+  public void testRemoveAllViaIterator() {
+    ArrayList<Integer> list = getRandomList(100, 123);
+    LightWeightGSet<TestElement, TestElement> set =
+        new LightWeightGSet<TestElement, TestElement>(16);
+    for (Integer i : list) {
+      set.put(new TestElement(i));
+    }
+    for (Iterator<TestElement> iter = set.iterator();
+        iter.hasNext(); ) {
+      iter.next();
+      iter.remove();
+    }
+    Assert.assertEquals(0, set.size());
+  }
+
+  @Test(timeout=60000)
+  public void testRemoveSomeViaIterator() {
+    ArrayList<Integer> list = getRandomList(100, 123);
+    LightWeightGSet<TestElement, TestElement> set =
+        new LightWeightGSet<TestElement, TestElement>(16);
+    for (Integer i : list) {
+      set.put(new TestElement(i));
+    }
+    long sum = 0;
+    for (Iterator<TestElement> iter = set.iterator();
+        iter.hasNext(); ) {
+      sum += iter.next().getVal();
+    }
+    long mode = sum / set.size();
+    LOG.info("Removing all elements above " + mode);
+    for (Iterator<TestElement> iter = set.iterator();
+        iter.hasNext(); ) {
+      int item = iter.next().getVal();
+      if (item > mode) {
+        iter.remove();
+      }
+    }
+    for (Iterator<TestElement> iter = set.iterator();
+        iter.hasNext(); ) {
+      Assert.assertTrue(iter.next().getVal() <= mode);
+    }
+  }
+}
diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES-HDFS-4949.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES-HDFS-4949.txt
new file mode 100644
index 0000000..7045860
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES-HDFS-4949.txt
@@ -0,0 +1,125 @@
+Hadoop HDFS Change Log for HDFS-4949
+
+HDFS-4949 (Unreleased)
+
+  INCOMPATIBLE CHANGES
+
+  NEW FEATURES
+
+  IMPROVEMENTS
+    HDFS-5049.  Add JNI mlock support.  (Andrew Wang via Colin Patrick McCabe)
+
+    HDFS-5051.  Propagate cache status information from the DataNode to the
+    NameNode  (Andrew Wang via Colin Patrick McCabe)
+
+    HDFS-5052.  Add cacheRequest/uncacheRequest support to NameNode.
+    (contributed by Colin Patrick McCabe)
+
+    HDFS-5050.  Add DataNode support for mlock and munlock
+    (Andrew Wang via Colin Patrick McCabe)
+
+    HDFS-5141. Add cache status information to datanode heartbeat.
+    (Contributed by Andrew Wang)
+
+    HDFS-5121. Add RPCs for creating and manipulating cache pools.
+    (Contributed by Colin Patrick McCabe)
+
+    HDFS-5163. Miscellaneous cache pool RPC fixes.  (Contributed by Colin
+    Patrick McCabe)
+
+    HDFS-5120. Add command-line support for manipulating cache pools.
+    (Contributed by Colin Patrick McCabe)
+
+    HDFS-5158. Add command-line support for manipulating cache directives.
+    (Contributed by Colin Patrick McCabe)
+
+    HDFS-5053. NameNode should invoke DataNode APIs to coordinate caching.
+    (Andrew Wang)
+
+    HDFS-5197. Document dfs.cachereport.intervalMsec in hdfs-default.xml.
+    (cnauroth)
+
+    HDFS-5213. Separate PathBasedCacheEntry and PathBasedCacheDirectiveWithId.
+    (Contributed by Colin Patrick McCabe)
+
+    HDFS-5236. Change PathBasedCacheDirective APIs to be a single value
+    rather than batch. (Contributed by Andrew Wang)
+
+    HDFS-5191. Revisit zero-copy API in FSDataInputStream to make it more
+    intuitive.  (Contributed by Colin Patrick McCabe)
+
+    HDFS-5119. Persist CacheManager state in the edit log.
+    (Contributed by Andrew Wang)
+
+    HDFS-5190. Move cache pool related CLI commands to CacheAdmin.
+    (Contributed by Andrew Wang)
+
+    HDFS-5304. Expose if a block replica is cached in getFileBlockLocations.
+    (Contributed by Andrew Wang)
+
+    HDFS-5224. Refactor PathBasedCache* methods to use a Path rather than a
+    String. (cnauroth)
+
+    HDFS-5358. Add replication field to PathBasedCacheDirective.
+    (Contributed by Colin Patrick McCabe)
+
+    HDFS-5359. Allow LightWeightGSet#Iterator to remove elements.
+    (Contributed by Colin Patrick McCabe)
+
+    HDFS-5096. Automatically cache new data added to a cached path.
+    (Contributed by Colin Patrick McCabe)
+
+    HDFS-5378. In CacheReport, don't send genstamp and length on the wire
+    (Contributed by Colin Patrick McCabe)
+
+  OPTIMIZATIONS
+    HDFS-5349. DNA_CACHE and DNA_UNCACHE should be by blockId only. (cmccabe)
+
+  BUG FIXES
+    HDFS-5169. hdfs.c: translateZCRException: null pointer deref when
+    translating some exceptions.  (Contributed by Colin Patrick McCabe)
+
+    HDFS-5198. NameNodeRpcServer must not send back DNA_FINALIZE in reply to a
+    cache report.  (Contributed by Colin Patrick McCabe)
+
+    HDFS-5195. Prevent passing null pointer to mlock and munlock. (cnauroth)
+
+    HDFS-5201. NativeIO: consolidate getrlimit into NativeIO#getMemlockLimit
+    (Contributed by Colin Patrick McCabe)
+
+    HDFS-5210. Fix some failing unit tests on HDFS-4949 branch.
+    (Contributed by Andrew Wang)
+
+    HDFS-5266. ElasticByteBufferPool#Key does not implement equals. (cnauroth)
+
+    HDFS-5309. Fix failing caching unit tests. (Andrew Wang)
+
+    HDFS-5314. Do not expose CachePool type in AddCachePoolOp (Colin Patrick
+    McCabe)
+
+    HDFS-5348. Fix error message when dfs.datanode.max.locked.memory is
+    improperly configured. (Colin Patrick McCabe)
+
+    HDFS-5373. hdfs cacheadmin -addDirective short usage does not mention
+    -replication parameter. (cnauroth)
+
+    HDFS-5383. fix broken caching unit tests. (Andrew Wang)
+
+    HDFS-5388. Loading fsimage fails to find cache pools during namenode
+    startup.  (Chris Nauroth via Colin Patrick McCabe)
+
+    HDFS-5203. Concurrent clients that add a cache directive on the same path
+    may prematurely uncache from each other.  (Chris Nauroth via Colin Patrick
+    McCabe)
+
+    HDFS-5385. Caching RPCs are AtMostOnce, but do not persist client ID and
+    call ID to edit log.  (Chris Nauroth via Colin Patrick McCabe)
+
+    HDFS-5404. Resolve regressions in Windows compatibility on HDFS-4949
+    branch. (Chris Nauroth via Andrew Wang)
+
+    HDFS-5405. Fix possible RetryCache hang for caching RPC handlers in
+    FSNamesystem. (wang)
+
+    HDFS-5419. Fixup test-patch.sh warnings on HDFS-4949 branch. (wang)
+
diff --git a/hadoop-hdfs-project/hadoop-hdfs/dev-support/findbugsExcludeFile.xml b/hadoop-hdfs-project/hadoop-hdfs/dev-support/findbugsExcludeFile.xml
index 77d9315..1c64505 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/dev-support/findbugsExcludeFile.xml
+++ b/hadoop-hdfs-project/hadoop-hdfs/dev-support/findbugsExcludeFile.xml
@@ -346,4 +346,22 @@
       <Method name="create" />
       <Bug pattern="UL_UNRELEASED_LOCK" />
     </Match>
+    <!-- Manually verified to be okay, we want to throw away the top bit here -->
+    <Match>
+      <Class name="org.apache.hadoop.hdfs.server.namenode.CachedBlock" />
+      <Method name="getReplication" />
+      <Bug pattern="ICAST_QUESTIONABLE_UNSIGNED_RIGHT_SHIFT" />
+    </Match>
+    <!-- These two are used for shutting down and kicking the CRMon, do not need strong sync -->
+    <Match>
+      <Class name="org.apache.hadoop.hdfs.server.blockmanagement.CacheReplicationMonitor" />
+      <Field name="shutdown" />
+      <Bug pattern="IS2_INCONSISTENT_SYNC" />
+    </Match>
+    <Match>
+      <Class name="org.apache.hadoop.hdfs.server.blockmanagement.CacheReplicationMonitor" />
+      <Field name="rescanImmediately" />
+      <Bug pattern="IS2_INCONSISTENT_SYNC" />
+    </Match>
+
  </FindBugsFilter>
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/bin/hdfs b/hadoop-hdfs-project/hadoop-hdfs/src/main/bin/hdfs
index c06a508..fa00cd4 100755
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/bin/hdfs
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/bin/hdfs
@@ -59,6 +59,7 @@
   echo "						Use -help to see options"
   echo "  portmap              run a portmap service"
   echo "  nfs3                 run an NFS version 3 gateway"
+  echo "  cacheadmin           configure the HDFS cache"
   echo ""
   echo "Most commands print help when invoked w/o parameters."
 }
@@ -155,6 +156,8 @@
   CLASS=org.apache.hadoop.portmap.Portmap
 elif [ "$COMMAND" = "nfs3" ] ; then
   CLASS=org.apache.hadoop.hdfs.nfs.nfs3.Nfs3
+elif [ "$COMMAND" = "cacheadmin" ] ; then
+  CLASS=org.apache.hadoop.hdfs.tools.CacheAdmin
 else
   CLASS="$COMMAND"
 fi
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSClient.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSClient.java
index 1e1b986..f62b6681 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSClient.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSClient.java
@@ -98,6 +98,7 @@
 import org.apache.hadoop.fs.MD5MD5CRC32FileChecksum;
 import org.apache.hadoop.fs.MD5MD5CRC32GzipFileChecksum;
 import org.apache.hadoop.fs.Options;
+import org.apache.hadoop.fs.RemoteIterator;
 import org.apache.hadoop.fs.Options.ChecksumOpt;
 import org.apache.hadoop.fs.ParentNotDirectoryException;
 import org.apache.hadoop.fs.Path;
@@ -107,6 +108,7 @@
 import org.apache.hadoop.hdfs.client.ClientMmapManager;
 import org.apache.hadoop.hdfs.client.HdfsDataInputStream;
 import org.apache.hadoop.hdfs.client.HdfsDataOutputStream;
+import org.apache.hadoop.hdfs.protocol.CachePoolInfo;
 import org.apache.hadoop.hdfs.protocol.ClientProtocol;
 import org.apache.hadoop.hdfs.protocol.CorruptFileBlocks;
 import org.apache.hadoop.hdfs.protocol.DSQuotaExceededException;
@@ -115,6 +117,8 @@
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
 import org.apache.hadoop.hdfs.protocol.HdfsBlocksMetadata;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDescriptor;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDirective;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants.DatanodeReportType;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants.SafeModeAction;
 import org.apache.hadoop.hdfs.protocol.HdfsFileStatus;
@@ -2286,7 +2290,73 @@
       throw re.unwrapRemoteException();
     }
   }
+
+  public PathBasedCacheDescriptor addPathBasedCacheDirective(
+      PathBasedCacheDirective directive) throws IOException {
+    checkOpen();
+    try {
+      return namenode.addPathBasedCacheDirective(directive);
+    } catch (RemoteException re) {
+      throw re.unwrapRemoteException();
+    }
+  }
   
+  public void removePathBasedCacheDescriptor(long id)
+      throws IOException {
+    checkOpen();
+    try {
+      namenode.removePathBasedCacheDescriptor(id);
+    } catch (RemoteException re) {
+      throw re.unwrapRemoteException();
+    }
+  }
+  
+  public RemoteIterator<PathBasedCacheDescriptor> listPathBasedCacheDescriptors(
+      String pool, String path) throws IOException {
+    checkOpen();
+    try {
+      return namenode.listPathBasedCacheDescriptors(0, pool, path);
+    } catch (RemoteException re) {
+      throw re.unwrapRemoteException();
+    }
+  }
+
+  public void addCachePool(CachePoolInfo info) throws IOException {
+    checkOpen();
+    try {
+      namenode.addCachePool(info);
+    } catch (RemoteException re) {
+      throw re.unwrapRemoteException();
+    }
+  }
+
+  public void modifyCachePool(CachePoolInfo info) throws IOException {
+    checkOpen();
+    try {
+      namenode.modifyCachePool(info);
+    } catch (RemoteException re) {
+      throw re.unwrapRemoteException();
+    }
+  }
+
+  public void removeCachePool(String poolName) throws IOException {
+    checkOpen();
+    try {
+      namenode.removeCachePool(poolName);
+    } catch (RemoteException re) {
+      throw re.unwrapRemoteException();
+    }
+  }
+
+  public RemoteIterator<CachePoolInfo> listCachePools() throws IOException {
+    checkOpen();
+    try {
+      return namenode.listCachePools("");
+    } catch (RemoteException re) {
+      throw re.unwrapRemoteException();
+    }
+  }
+
   /**
    * Save namespace image.
    * 
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java
index 0f9c824..8bca957 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java
@@ -99,6 +99,12 @@
   public static final boolean DFS_DATANODE_DROP_CACHE_BEHIND_READS_DEFAULT = false;
   public static final String  DFS_DATANODE_USE_DN_HOSTNAME = "dfs.datanode.use.datanode.hostname";
   public static final boolean DFS_DATANODE_USE_DN_HOSTNAME_DEFAULT = false;
+  public static final String  DFS_DATANODE_MAX_LOCKED_MEMORY_KEY = "dfs.datanode.max.locked.memory";
+  public static final long    DFS_DATANODE_MAX_LOCKED_MEMORY_DEFAULT = 0;
+  public static final String  DFS_DATANODE_FSDATASETCACHE_MAX_THREADS_PER_VOLUME_KEY = "dfs.datanode.fsdatasetcache.max.threads.per.volume";
+  public static final int     DFS_DATANODE_FSDATASETCACHE_MAX_THREADS_PER_VOLUME_DEFAULT = 4;
+  public static final String  DFS_NAMENODE_CACHING_ENABLED_KEY = "dfs.namenode.caching.enabled";
+  public static final boolean DFS_NAMENODE_CACHING_ENABLED_DEFAULT = false;
 
   public static final String  DFS_NAMENODE_HTTP_PORT_KEY = "dfs.http.port";
   public static final int     DFS_NAMENODE_HTTP_PORT_DEFAULT = 50070;
@@ -197,6 +203,16 @@
   public static final String DFS_NAMENODE_DATANODE_REGISTRATION_IP_HOSTNAME_CHECK_KEY = "dfs.namenode.datanode.registration.ip-hostname-check";
   public static final boolean DFS_NAMENODE_DATANODE_REGISTRATION_IP_HOSTNAME_CHECK_DEFAULT = true;
 
+  public static final String  DFS_NAMENODE_LIST_CACHE_POOLS_NUM_RESPONSES =
+      "dfs.namenode.list.cache.pools.num.responses";
+  public static final int     DFS_NAMENODE_LIST_CACHE_POOLS_NUM_RESPONSES_DEFAULT = 100;
+  public static final String  DFS_NAMENODE_LIST_CACHE_DESCRIPTORS_NUM_RESPONSES =
+      "dfs.namenode.list.cache.descriptors.num.responses";
+  public static final int     DFS_NAMENODE_LIST_CACHE_DESCRIPTORS_NUM_RESPONSES_DEFAULT = 100;
+  public static final String  DFS_NAMENODE_PATH_BASED_CACHE_REFRESH_INTERVAL_MS =
+      "dfs.namenode.path.based.cache.refresh.interval.ms";
+  public static final long    DFS_NAMENODE_PATH_BASED_CACHE_REFRESH_INTERVAL_MS_DEFAULT = 300000L;
+
   // Whether to enable datanode's stale state detection and usage for reads
   public static final String DFS_NAMENODE_AVOID_STALE_DATANODE_FOR_READ_KEY = "dfs.namenode.avoid.read.stale.datanode";
   public static final boolean DFS_NAMENODE_AVOID_STALE_DATANODE_FOR_READ_DEFAULT = false;
@@ -362,6 +378,8 @@
   public static final long    DFS_BLOCKREPORT_INTERVAL_MSEC_DEFAULT = 60 * 60 * 1000;
   public static final String  DFS_BLOCKREPORT_INITIAL_DELAY_KEY = "dfs.blockreport.initialDelay";
   public static final int     DFS_BLOCKREPORT_INITIAL_DELAY_DEFAULT = 0;
+  public static final String  DFS_CACHEREPORT_INTERVAL_MSEC_KEY = "dfs.cachereport.intervalMsec";
+  public static final long    DFS_CACHEREPORT_INTERVAL_MSEC_DEFAULT = 10 * 1000;
   public static final String  DFS_BLOCK_INVALIDATE_LIMIT_KEY = "dfs.block.invalidate.limit";
   public static final int     DFS_BLOCK_INVALIDATE_LIMIT_DEFAULT = 1000;
   public static final String  DFS_DEFAULT_MAX_CORRUPT_FILES_RETURNED_KEY = "dfs.corruptfilesreturned.max";
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DistributedFileSystem.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DistributedFileSystem.java
index 6fb572a..d2d3168 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DistributedFileSystem.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DistributedFileSystem.java
@@ -57,6 +57,7 @@
 import org.apache.hadoop.hdfs.client.HdfsAdmin;
 import org.apache.hadoop.hdfs.client.HdfsDataInputStream;
 import org.apache.hadoop.hdfs.client.HdfsDataOutputStream;
+import org.apache.hadoop.hdfs.protocol.CachePoolInfo;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
 import org.apache.hadoop.hdfs.protocol.DirectoryListing;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
@@ -66,6 +67,8 @@
 import org.apache.hadoop.hdfs.protocol.HdfsFileStatus;
 import org.apache.hadoop.hdfs.protocol.HdfsLocatedFileStatus;
 import org.apache.hadoop.hdfs.protocol.LocatedBlock;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDirective;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDescriptor;
 import org.apache.hadoop.hdfs.protocol.SnapshotDiffReport;
 import org.apache.hadoop.hdfs.protocol.SnapshottableDirectoryStatus;
 import org.apache.hadoop.hdfs.security.token.block.InvalidBlockTokenException;
@@ -1579,5 +1582,113 @@
       }
     }.resolve(this, absF);
   }
+
+  /**
+   * Add a new PathBasedCacheDirective.
+   * 
+   * @param directive A PathBasedCacheDirectives to add
+   * @return PathBasedCacheDescriptor associated with the added directive
+   * @throws IOException if the directive could not be added
+   */
+  public PathBasedCacheDescriptor addPathBasedCacheDirective(
+      PathBasedCacheDirective directive) throws IOException {
+    Path path = new Path(getPathName(fixRelativePart(directive.getPath()))).
+        makeQualified(getUri(), getWorkingDirectory());
+    return dfs.addPathBasedCacheDirective(new PathBasedCacheDirective.Builder().
+        setPath(path).
+        setReplication(directive.getReplication()).
+        setPool(directive.getPool()).
+        build());
+  }
   
+  /**
+   * Remove a PathBasedCacheDescriptor.
+   * 
+   * @param descriptor PathBasedCacheDescriptor to remove
+   * @throws IOException if the descriptor could not be removed
+   */
+  public void removePathBasedCacheDescriptor(PathBasedCacheDescriptor descriptor)
+      throws IOException {
+    dfs.removePathBasedCacheDescriptor(descriptor.getEntryId());
+  }
+  
+  /**
+   * List the set of cached paths of a cache pool. Incrementally fetches results
+   * from the server.
+   * 
+   * @param pool The cache pool to list, or null to list all pools.
+   * @param path The path name to list, or null to list all paths.
+   * @return A RemoteIterator which returns PathBasedCacheDescriptor objects.
+   */
+  public RemoteIterator<PathBasedCacheDescriptor> listPathBasedCacheDescriptors(
+      String pool, final Path path) throws IOException {
+    String pathName = path != null ? getPathName(fixRelativePart(path)) : null;
+    final RemoteIterator<PathBasedCacheDescriptor> iter =
+        dfs.listPathBasedCacheDescriptors(pool, pathName);
+    return new RemoteIterator<PathBasedCacheDescriptor>() {
+      @Override
+      public boolean hasNext() throws IOException {
+        return iter.hasNext();
+      }
+
+      @Override
+      public PathBasedCacheDescriptor next() throws IOException {
+        PathBasedCacheDescriptor desc = iter.next();
+        Path qualPath = desc.getPath().makeQualified(getUri(), path);
+        return new PathBasedCacheDescriptor(desc.getEntryId(), qualPath,
+            desc.getReplication(), desc.getPool());
+      }
+    };
+  }
+
+  /**
+   * Add a cache pool.
+   *
+   * @param info
+   *          The request to add a cache pool.
+   * @throws IOException 
+   *          If the request could not be completed.
+   */
+  public void addCachePool(CachePoolInfo info) throws IOException {
+    CachePoolInfo.validate(info);
+    dfs.addCachePool(info);
+  }
+
+  /**
+   * Modify an existing cache pool.
+   *
+   * @param info
+   *          The request to modify a cache pool.
+   * @throws IOException 
+   *          If the request could not be completed.
+   */
+  public void modifyCachePool(CachePoolInfo info) throws IOException {
+    CachePoolInfo.validate(info);
+    dfs.modifyCachePool(info);
+  }
+    
+  /**
+   * Remove a cache pool.
+   *
+   * @param poolName
+   *          Name of the cache pool to remove.
+   * @throws IOException 
+   *          if the cache pool did not exist, or could not be removed.
+   */
+  public void removeCachePool(String poolName) throws IOException {
+    CachePoolInfo.validateName(poolName);
+    dfs.removeCachePool(poolName);
+  }
+
+  /**
+   * List all cache pools.
+   *
+   * @return A remote iterator from which you can get CachePoolInfo objects.
+   *          Requests will be made as needed.
+   * @throws IOException
+   *          If there was an error listing cache pools.
+   */
+  public RemoteIterator<CachePoolInfo> listCachePools() throws IOException {
+    return dfs.listCachePools();
+  }
 }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/AddPathBasedCacheDirectiveException.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/AddPathBasedCacheDirectiveException.java
new file mode 100644
index 0000000..a59463d
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/AddPathBasedCacheDirectiveException.java
@@ -0,0 +1,108 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.protocol;
+
+import java.io.IOException;
+
+/**
+ * An exception which occurred when trying to add a PathBasedCache directive.
+ */
+public abstract class AddPathBasedCacheDirectiveException extends IOException {
+  private static final long serialVersionUID = 1L;
+
+  public AddPathBasedCacheDirectiveException(String description) {
+    super(description);
+  }
+
+  public static final class EmptyPathError
+      extends AddPathBasedCacheDirectiveException {
+    private static final long serialVersionUID = 1L;
+
+    public EmptyPathError() {
+      super("empty path in directive");
+    }
+  }
+
+  public static class InvalidPathNameError
+      extends AddPathBasedCacheDirectiveException {
+    private static final long serialVersionUID = 1L;
+
+    public InvalidPathNameError(String msg) {
+      super(msg);
+    }
+
+    public InvalidPathNameError(PathBasedCacheDirective directive) {
+      this("can't handle invalid path name " + directive.getPath());
+    }
+  }
+
+  public static class InvalidPoolNameError
+      extends AddPathBasedCacheDirectiveException {
+    private static final long serialVersionUID = 1L;
+
+    public InvalidPoolNameError(String msg) {
+      super(msg);
+    }
+
+    public InvalidPoolNameError(PathBasedCacheDirective directive) {
+      this("invalid pool name '" + directive.getPool() + "'");
+    }
+  }
+
+  public static class PoolWritePermissionDeniedError
+      extends AddPathBasedCacheDirectiveException {
+    private static final long serialVersionUID = 1L;
+
+    public PoolWritePermissionDeniedError(String msg) {
+      super(msg);
+    }
+
+    public PoolWritePermissionDeniedError(PathBasedCacheDirective directive) {
+      this("write permission denied for pool '" + directive.getPool() + "'");
+    }
+  }
+
+  public static class PathAlreadyExistsInPoolError
+      extends AddPathBasedCacheDirectiveException {
+    private static final long serialVersionUID = 1L;
+
+    public PathAlreadyExistsInPoolError(String msg) {
+      super(msg);
+    }
+
+    public PathAlreadyExistsInPoolError(PathBasedCacheDirective directive) {
+      this("path " + directive.getPath() + " already exists in pool " +
+          directive.getPool());
+    }
+  }
+
+  public static class UnexpectedAddPathBasedCacheDirectiveException
+      extends AddPathBasedCacheDirectiveException {
+    private static final long serialVersionUID = 1L;
+
+    public UnexpectedAddPathBasedCacheDirectiveException(String msg) {
+      super(msg);
+    }
+
+    public UnexpectedAddPathBasedCacheDirectiveException(
+        PathBasedCacheDirective directive) {
+      this("encountered an unexpected error when trying to " +
+          "add PathBasedCache directive " + directive);
+    }
+  }
+}
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/CachePoolInfo.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/CachePoolInfo.java
new file mode 100644
index 0000000..e944d3c
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/CachePoolInfo.java
@@ -0,0 +1,228 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.hdfs.protocol;
+
+import java.io.DataInput;
+import java.io.DataOutput;
+import java.io.IOException;
+
+import javax.annotation.Nullable;
+
+import org.apache.commons.lang.builder.EqualsBuilder;
+import org.apache.commons.lang.builder.HashCodeBuilder;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+import org.apache.hadoop.fs.permission.FsPermission;
+import org.apache.hadoop.fs.permission.PermissionStatus;
+import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp;
+import org.apache.hadoop.hdfs.util.XMLUtils;
+import org.apache.hadoop.hdfs.util.XMLUtils.InvalidXmlException;
+import org.apache.hadoop.hdfs.util.XMLUtils.Stanza;
+import org.apache.hadoop.io.Text;
+import org.xml.sax.ContentHandler;
+import org.xml.sax.SAXException;
+
+/**
+ * CachePoolInfo describes a cache pool.
+ *
+ * This class is used in RPCs to create and modify cache pools.
+ * It is serializable and can be stored in the edit log.
+ */
+@InterfaceAudience.Private
+@InterfaceStability.Evolving
+public class CachePoolInfo {
+  public static final Log LOG = LogFactory.getLog(CachePoolInfo.class);
+
+  final String poolName;
+
+  @Nullable
+  String ownerName;
+
+  @Nullable
+  String groupName;
+
+  @Nullable
+  FsPermission mode;
+
+  @Nullable
+  Integer weight;
+
+  public CachePoolInfo(String poolName) {
+    this.poolName = poolName;
+  }
+  
+  public String getPoolName() {
+    return poolName;
+  }
+
+  public String getOwnerName() {
+    return ownerName;
+  }
+
+  public CachePoolInfo setOwnerName(String ownerName) {
+    this.ownerName = ownerName;
+    return this;
+  }
+
+  public String getGroupName() {
+    return groupName;
+  }
+
+  public CachePoolInfo setGroupName(String groupName) {
+    this.groupName = groupName;
+    return this;
+  }
+  
+  public FsPermission getMode() {
+    return mode;
+  }
+
+  public CachePoolInfo setMode(FsPermission mode) {
+    this.mode = mode;
+    return this;
+  }
+
+  public Integer getWeight() {
+    return weight;
+  }
+
+  public CachePoolInfo setWeight(Integer weight) {
+    this.weight = weight;
+    return this;
+  }
+
+  public String toString() {
+    return new StringBuilder().append("{").
+      append("poolName:").append(poolName).
+      append(", ownerName:").append(ownerName).
+      append(", groupName:").append(groupName).
+      append(", mode:").append((mode == null) ? "null" :
+          String.format("0%03o", mode.toShort())).
+      append(", weight:").append(weight).
+      append("}").toString();
+  }
+  
+  @Override
+  public boolean equals(Object o) {
+    if (o == null) { return false; }
+    if (o == this) { return true; }
+    if (o.getClass() != getClass()) {
+      return false;
+    }
+    CachePoolInfo other = (CachePoolInfo)o;
+    return new EqualsBuilder().
+        append(poolName, other.poolName).
+        append(ownerName, other.ownerName).
+        append(groupName, other.groupName).
+        append(mode, other.mode).
+        append(weight, other.weight).
+        isEquals();
+  }
+
+  @Override
+  public int hashCode() {
+    return new HashCodeBuilder().
+        append(poolName).
+        append(ownerName).
+        append(groupName).
+        append(mode).
+        append(weight).
+        hashCode();
+  }
+
+  public static void validate(CachePoolInfo info) throws IOException {
+    if (info == null) {
+      throw new IOException("CachePoolInfo is null");
+    }
+    validateName(info.poolName);
+  }
+
+  public static void validateName(String poolName) throws IOException {
+    if (poolName == null || poolName.isEmpty()) {
+      // Empty pool names are not allowed because they would be highly
+      // confusing.  They would also break the ability to list all pools
+      // by starting with prevKey = ""
+      throw new IOException("invalid empty cache pool name");
+    }
+  }
+
+  public static CachePoolInfo readFrom(DataInput in) throws IOException {
+    String poolName = Text.readString(in);
+    CachePoolInfo info = new CachePoolInfo(poolName);
+    if (in.readBoolean()) {
+      info.setOwnerName(Text.readString(in));
+    }
+    if (in.readBoolean())  {
+      info.setGroupName(Text.readString(in));
+    }
+    if (in.readBoolean()) {
+      info.setMode(FsPermission.read(in));
+    }
+    if (in.readBoolean()) {
+      info.setWeight(in.readInt());
+    }
+    return info;
+  }
+
+  public void writeTo(DataOutput out) throws IOException {
+    Text.writeString(out, poolName);
+    boolean hasOwner, hasGroup, hasMode, hasWeight;
+    hasOwner = ownerName != null;
+    hasGroup = groupName != null;
+    hasMode = mode != null;
+    hasWeight = weight != null;
+    out.writeBoolean(hasOwner);
+    if (hasOwner) {
+      Text.writeString(out, ownerName);
+    }
+    out.writeBoolean(hasGroup);
+    if (hasGroup) {
+      Text.writeString(out, groupName);
+    }
+    out.writeBoolean(hasMode);
+    if (hasMode) {
+      mode.write(out);
+    }
+    out.writeBoolean(hasWeight);
+    if (hasWeight) {
+      out.writeInt(weight);
+    }
+  }
+
+  public void writeXmlTo(ContentHandler contentHandler) throws SAXException {
+    XMLUtils.addSaxString(contentHandler, "POOLNAME", poolName);
+    PermissionStatus perm = new PermissionStatus(ownerName,
+        groupName, mode);
+    FSEditLogOp.permissionStatusToXml(contentHandler, perm);
+    XMLUtils.addSaxString(contentHandler, "WEIGHT", Integer.toString(weight));
+  }
+
+  public static CachePoolInfo readXmlFrom(Stanza st) throws InvalidXmlException {
+    String poolName = st.getValue("POOLNAME");
+    PermissionStatus perm = FSEditLogOp.permissionStatusFromXml(st);
+    int weight = Integer.parseInt(st.getValue("WEIGHT"));
+    return new CachePoolInfo(poolName).
+        setOwnerName(perm.getUserName()).
+        setGroupName(perm.getGroupName()).
+        setMode(perm.getPermission()).
+        setWeight(weight);
+  }
+}
\ No newline at end of file
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/ClientProtocol.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/ClientProtocol.java
index 5789c36..f7d2272 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/ClientProtocol.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/ClientProtocol.java
@@ -30,6 +30,7 @@
 import org.apache.hadoop.fs.Options;
 import org.apache.hadoop.fs.Options.Rename;
 import org.apache.hadoop.fs.ParentNotDirectoryException;
+import org.apache.hadoop.fs.RemoteIterator;
 import org.apache.hadoop.fs.UnresolvedLinkException;
 import org.apache.hadoop.fs.permission.FsPermission;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
@@ -1093,5 +1094,79 @@
   @Idempotent
   public SnapshotDiffReport getSnapshotDiffReport(String snapshotRoot,
       String fromSnapshot, String toSnapshot) throws IOException;
-}
 
+  /**
+   * Add a PathBasedCache entry to the CacheManager.
+   * 
+   * @param directive A PathBasedCacheDirective to be added
+   * @return A PathBasedCacheDescriptor associated with the added directive
+   * @throws IOException if the directive could not be added
+   */
+  @AtMostOnce
+  public PathBasedCacheDescriptor addPathBasedCacheDirective(
+      PathBasedCacheDirective directive) throws IOException;
+
+  /**
+   * Remove a PathBasedCacheDescriptor from the CacheManager.
+   * 
+   * @param id of a PathBasedCacheDescriptor
+   * @throws IOException if the cache descriptor could not be removed
+   */
+  @AtMostOnce
+  public void removePathBasedCacheDescriptor(Long id) throws IOException;
+
+  /**
+   * List the set of cached paths of a cache pool. Incrementally fetches results
+   * from the server.
+   * 
+   * @param prevId The last listed entry ID, or -1 if this is the first call to
+   *          listPathBasedCacheDescriptors.
+   * @param pool The cache pool to list, or null to list all pools.
+   * @param path The path name to list, or null to list all paths.
+   * @return A RemoteIterator which returns PathBasedCacheDescriptor objects.
+   */
+  @Idempotent
+  public RemoteIterator<PathBasedCacheDescriptor> listPathBasedCacheDescriptors(
+      long prevId, String pool, String path) throws IOException;
+
+  /**
+   * Add a new cache pool.
+   * 
+   * @param info Description of the new cache pool
+   * @throws IOException If the request could not be completed.
+   */
+  @AtMostOnce
+  public void addCachePool(CachePoolInfo info) throws IOException;
+
+  /**
+   * Modify an existing cache pool.
+   *
+   * @param req
+   *          The request to modify a cache pool.
+   * @throws IOException 
+   *          If the request could not be completed.
+   */
+  @AtMostOnce
+  public void modifyCachePool(CachePoolInfo req) throws IOException;
+  
+  /**
+   * Remove a cache pool.
+   * 
+   * @param pool name of the cache pool to remove.
+   * @throws IOException if the cache pool did not exist, or could not be
+   *           removed.
+   */
+  @AtMostOnce
+  public void removeCachePool(String pool) throws IOException;
+
+  /**
+   * List the set of cache pools. Incrementally fetches results from the server.
+   * 
+   * @param prevPool name of the last pool listed, or the empty string if this is
+   *          the first invocation of listCachePools
+   * @return A RemoteIterator which returns CachePool objects.
+   */
+  @Idempotent
+  public RemoteIterator<CachePoolInfo> listCachePools(String prevPool)
+      throws IOException;
+}
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/DatanodeInfo.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/DatanodeInfo.java
index 1d2bbab..17636ed1 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/DatanodeInfo.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/DatanodeInfo.java
@@ -44,6 +44,8 @@
   private long dfsUsed;
   private long remaining;
   private long blockPoolUsed;
+  private long cacheCapacity;
+  private long cacheUsed;
   private long lastUpdate;
   private int xceiverCount;
   private String location = NetworkTopology.DEFAULT_RACK;
@@ -82,6 +84,8 @@
     this.dfsUsed = from.getDfsUsed();
     this.remaining = from.getRemaining();
     this.blockPoolUsed = from.getBlockPoolUsed();
+    this.cacheCapacity = from.getCacheCapacity();
+    this.cacheUsed = from.getCacheUsed();
     this.lastUpdate = from.getLastUpdate();
     this.xceiverCount = from.getXceiverCount();
     this.location = from.getNetworkLocation();
@@ -94,6 +98,8 @@
     this.dfsUsed = 0L;
     this.remaining = 0L;
     this.blockPoolUsed = 0L;
+    this.cacheCapacity = 0L;
+    this.cacheUsed = 0L;
     this.lastUpdate = 0L;
     this.xceiverCount = 0;
     this.adminState = null;    
@@ -106,12 +112,14 @@
   
   public DatanodeInfo(DatanodeID nodeID, String location,
       final long capacity, final long dfsUsed, final long remaining,
-      final long blockPoolUsed, final long lastUpdate, final int xceiverCount,
+      final long blockPoolUsed, final long cacheCapacity, final long cacheUsed,
+      final long lastUpdate, final int xceiverCount,
       final AdminStates adminState) {
     this(nodeID.getIpAddr(), nodeID.getHostName(), nodeID.getStorageID(),
         nodeID.getXferPort(), nodeID.getInfoPort(), nodeID.getInfoSecurePort(),
         nodeID.getIpcPort(), capacity, dfsUsed, remaining, blockPoolUsed,
-        lastUpdate, xceiverCount, location, adminState);
+        cacheCapacity, cacheUsed, lastUpdate, xceiverCount, location,
+        adminState);
   }
 
   /** Constructor */
@@ -119,7 +127,8 @@
       final String storageID, final int xferPort, final int infoPort,
       final int infoSecurePort, final int ipcPort,
       final long capacity, final long dfsUsed, final long remaining,
-      final long blockPoolUsed, final long lastUpdate, final int xceiverCount,
+      final long blockPoolUsed, final long cacheCapacity, final long cacheUsed,
+      final long lastUpdate, final int xceiverCount,
       final String networkLocation, final AdminStates adminState) {
     super(ipAddr, hostName, storageID, xferPort, infoPort,
             infoSecurePort, ipcPort);
@@ -127,6 +136,8 @@
     this.dfsUsed = dfsUsed;
     this.remaining = remaining;
     this.blockPoolUsed = blockPoolUsed;
+    this.cacheCapacity = cacheCapacity;
+    this.cacheUsed = cacheUsed;
     this.lastUpdate = lastUpdate;
     this.xceiverCount = xceiverCount;
     this.location = networkLocation;
@@ -172,6 +183,42 @@
     return DFSUtil.getPercentRemaining(remaining, capacity);
   }
 
+  /**
+   * @return Amount of cache capacity in bytes
+   */
+  public long getCacheCapacity() {
+    return cacheCapacity;
+  }
+
+  /**
+   * @return Amount of cache used in bytes
+   */
+  public long getCacheUsed() {
+    return cacheUsed;
+  }
+
+  /**
+   * @return Cache used as a percentage of the datanode's total cache capacity
+   */
+  public float getCacheUsedPercent() {
+    return DFSUtil.getPercentUsed(cacheUsed, cacheCapacity);
+  }
+
+  /**
+   * @return Amount of cache remaining in bytes
+   */
+  public long getCacheRemaining() {
+    return cacheCapacity - cacheUsed;
+  }
+
+  /**
+   * @return Cache remaining as a percentage of the datanode's total cache
+   * capacity
+   */
+  public float getCacheRemainingPercent() {
+    return DFSUtil.getPercentRemaining(getCacheRemaining(), cacheCapacity);
+  }
+
   /** The time when this information was accurate. */
   public long getLastUpdate() { return lastUpdate; }
 
@@ -198,6 +245,16 @@
     this.blockPoolUsed = bpUsed; 
   }
 
+  /** Sets cache capacity. */
+  public void setCacheCapacity(long cacheCapacity) {
+    this.cacheCapacity = cacheCapacity;
+  }
+
+  /** Sets cache used. */
+  public void setCacheUsed(long cacheUsed) {
+    this.cacheUsed = cacheUsed;
+  }
+
   /** Sets time when this information was accurate. */
   public void setLastUpdate(long lastUpdate) { 
     this.lastUpdate = lastUpdate; 
@@ -227,6 +284,11 @@
     long nonDFSUsed = getNonDfsUsed();
     float usedPercent = getDfsUsedPercent();
     float remainingPercent = getRemainingPercent();
+    long cc = getCacheCapacity();
+    long cr = getCacheRemaining();
+    long cu = getCacheUsed();
+    float cacheUsedPercent = getCacheUsedPercent();
+    float cacheRemainingPercent = getCacheRemainingPercent();
     String lookupName = NetUtils.getHostNameOfIP(getName());
 
     buffer.append("Name: "+ getName());
@@ -253,6 +315,12 @@
     buffer.append("DFS Remaining: " +r+ " ("+StringUtils.byteDesc(r)+")"+"\n");
     buffer.append("DFS Used%: "+percent2String(usedPercent) + "\n");
     buffer.append("DFS Remaining%: "+percent2String(remainingPercent) + "\n");
+    buffer.append("Configured Cache Capacity: "+c+" ("+StringUtils.byteDesc(cc)+")"+"\n");
+    buffer.append("Cache Used: "+cu+" ("+StringUtils.byteDesc(u)+")"+"\n");
+    buffer.append("Cache Remaining: " +cr+ " ("+StringUtils.byteDesc(r)+")"+"\n");
+    buffer.append("Cache Used%: "+percent2String(cacheUsedPercent) + "\n");
+    buffer.append("Cache Remaining%: "+percent2String(cacheRemainingPercent) + "\n");
+
     buffer.append("Last contact: "+new Date(lastUpdate)+"\n");
     return buffer.toString();
   }
@@ -263,6 +331,9 @@
     long c = getCapacity();
     long r = getRemaining();
     long u = getDfsUsed();
+    long cc = getCacheCapacity();
+    long cr = getCacheRemaining();
+    long cu = getCacheUsed();
     buffer.append(getName());
     if (!NetworkTopology.DEFAULT_RACK.equals(location)) {
       buffer.append(" "+location);
@@ -278,6 +349,10 @@
     buffer.append(" " + u + "(" + StringUtils.byteDesc(u)+")");
     buffer.append(" " + percent2String(u/(double)c));
     buffer.append(" " + r + "(" + StringUtils.byteDesc(r)+")");
+    buffer.append(" " + cc + "(" + StringUtils.byteDesc(cc)+")");
+    buffer.append(" " + cu + "(" + StringUtils.byteDesc(cu)+")");
+    buffer.append(" " + percent2String(cu/(double)cc));
+    buffer.append(" " + cr + "(" + StringUtils.byteDesc(cr)+")");
     buffer.append(" " + new Date(lastUpdate));
     return buffer.toString();
   }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/LayoutVersion.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/LayoutVersion.java
index d4c62c4..09333e5 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/LayoutVersion.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/LayoutVersion.java
@@ -106,7 +106,8 @@
     SEQUENTIAL_BLOCK_ID(-46, "Allocate block IDs sequentially and store " +
         "block IDs in the edits log and image files"),
     EDITLOG_SUPPORT_RETRYCACHE(-47, "Record ClientId and CallId in editlog to " 
-        + "enable rebuilding retry cache in case of HA failover");
+        + "enable rebuilding retry cache in case of HA failover"),
+    CACHING(-48, "Support for cache pools and path-based caching");
     
     final int lv;
     final int ancestorLV;
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/LocatedBlock.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/LocatedBlock.java
index d9da5b8..ddd39d1c 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/LocatedBlock.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/LocatedBlock.java
@@ -17,15 +17,21 @@
  */
 package org.apache.hadoop.hdfs.protocol;
 
+import java.util.List;
+
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
 import org.apache.hadoop.hdfs.security.token.block.BlockTokenIdentifier;
 import org.apache.hadoop.security.token.Token;
 
+import com.google.common.base.Preconditions;
+import com.google.common.collect.Lists;
+
 /**
  * Associates a block with the Datanodes that contain its replicas
  * and other block metadata (E.g. the file offset associated with this
- * block, whether it is corrupt, security token, etc).
+ * block, whether it is corrupt, a location is cached in memory,
+ * security token, etc).
  */
 @InterfaceAudience.Private
 @InterfaceStability.Evolving
@@ -39,9 +45,16 @@
   // their locations are not part of this object
   private boolean corrupt;
   private Token<BlockTokenIdentifier> blockToken = new Token<BlockTokenIdentifier>();
+  /**
+   * List of cached datanode locations
+   */
+  private DatanodeInfo[] cachedLocs;
+
+  // Used when there are no locations
+  private static final DatanodeInfo[] EMPTY_LOCS = new DatanodeInfo[0];
 
   public LocatedBlock(ExtendedBlock b, DatanodeInfo[] locs) {
-    this(b, locs, -1, false); // startOffset is unknown
+    this(b, locs, -1); // startOffset is unknown
   }
 
   public LocatedBlock(ExtendedBlock b, DatanodeInfo[] locs, long startOffset) {
@@ -50,14 +63,26 @@
 
   public LocatedBlock(ExtendedBlock b, DatanodeInfo[] locs, long startOffset, 
                       boolean corrupt) {
+    this(b, locs, startOffset, corrupt, EMPTY_LOCS);
+  }
+
+  public LocatedBlock(ExtendedBlock b, DatanodeInfo[] locs, long startOffset,
+      boolean corrupt, DatanodeInfo[] cachedLocs) {
     this.b = b;
     this.offset = startOffset;
     this.corrupt = corrupt;
     if (locs==null) {
-      this.locs = new DatanodeInfo[0];
+      this.locs = EMPTY_LOCS;
     } else {
       this.locs = locs;
     }
+    Preconditions.checkArgument(cachedLocs != null,
+        "cachedLocs should not be null, use a different constructor");
+    if (cachedLocs.length == 0) {
+      this.cachedLocs = EMPTY_LOCS;
+    } else {
+      this.cachedLocs = cachedLocs;
+    }
   }
 
   public Token<BlockTokenIdentifier> getBlockToken() {
@@ -96,6 +121,36 @@
     return this.corrupt;
   }
 
+  /**
+   * Add a the location of a cached replica of the block.
+   * 
+   * @param loc of datanode with the cached replica
+   */
+  public void addCachedLoc(DatanodeInfo loc) {
+    List<DatanodeInfo> cachedList = Lists.newArrayList(cachedLocs);
+    if (cachedList.contains(loc)) {
+      return;
+    }
+    // Try to re-use a DatanodeInfo already in loc
+    for (int i=0; i<locs.length; i++) {
+      if (locs[i].equals(loc)) {
+        cachedList.add(locs[i]);
+        cachedLocs = cachedList.toArray(cachedLocs);
+        return;
+      }
+    }
+    // Not present in loc, add it and go
+    cachedList.add(loc);
+    cachedLocs = cachedList.toArray(cachedLocs);
+  }
+
+  /**
+   * @return Datanodes with a cached block replica
+   */
+  public DatanodeInfo[] getCachedLocations() {
+    return cachedLocs;
+  }
+
   @Override
   public String toString() {
     return getClass().getSimpleName() + "{" + b
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/PathBasedCacheDescriptor.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/PathBasedCacheDescriptor.java
new file mode 100644
index 0000000..6e60a9b
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/PathBasedCacheDescriptor.java
@@ -0,0 +1,82 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.protocol;
+
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+import org.apache.hadoop.fs.Path;
+import org.apache.commons.lang.builder.EqualsBuilder;
+import org.apache.commons.lang.builder.HashCodeBuilder;
+
+import com.google.common.base.Preconditions;
+
+/**
+ * A directive in a cache pool that includes an identifying ID number.
+ */
+@InterfaceStability.Evolving
+@InterfaceAudience.Public
+public final class PathBasedCacheDescriptor extends PathBasedCacheDirective {
+  private final long entryId;
+
+  public PathBasedCacheDescriptor(long entryId, Path path,
+      short replication, String pool) {
+    super(path, replication, pool);
+    Preconditions.checkArgument(entryId > 0);
+    this.entryId = entryId;
+  }
+
+  public long getEntryId() {
+    return entryId;
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    if (o == null) {
+      return false;
+    }
+    if (getClass() != o.getClass()) {
+      return false;
+    }
+    PathBasedCacheDescriptor other = (PathBasedCacheDescriptor)o;
+    return new EqualsBuilder().append(entryId, other.entryId).
+        append(getPath(), other.getPath()).
+        append(getReplication(), other.getReplication()).
+        append(getPool(), other.getPool()).
+        isEquals();
+  }
+
+  @Override
+  public int hashCode() {
+    return new HashCodeBuilder().append(entryId).
+        append(getPath()).
+        append(getReplication()).
+        append(getPool()).
+        hashCode();
+  }
+
+  @Override
+  public String toString() {
+    StringBuilder builder = new StringBuilder();
+    builder.append("{ entryId:").append(entryId).
+      append(", path:").append(getPath()).
+      append(", replication:").append(getReplication()).
+      append(", pool:").append(getPool()).
+      append(" }");
+    return builder.toString();
+  }
+};
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/PathBasedCacheDirective.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/PathBasedCacheDirective.java
new file mode 100644
index 0000000..b25b039
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/PathBasedCacheDirective.java
@@ -0,0 +1,182 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.protocol;
+
+import java.io.IOException;
+
+import com.google.common.base.Preconditions;
+
+import org.apache.commons.lang.builder.EqualsBuilder;
+import org.apache.commons.lang.builder.HashCodeBuilder;
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hdfs.DFSUtil;
+import org.apache.hadoop.hdfs.protocol.AddPathBasedCacheDirectiveException.InvalidPoolNameError;
+import org.apache.hadoop.hdfs.protocol.AddPathBasedCacheDirectiveException.InvalidPathNameError;
+
+/**
+ * A directive to add a path to a cache pool.
+ */
+@InterfaceStability.Evolving
+@InterfaceAudience.Public
+public class PathBasedCacheDirective {
+
+  /**
+   * A builder for creating new PathBasedCacheDirective instances.
+   */
+  public static class Builder {
+    private Path path;
+    private short replication = (short)1;
+    private String pool;
+
+    /**
+     * Builds a new PathBasedCacheDirective populated with the set properties.
+     * 
+     * @return New PathBasedCacheDirective.
+     */
+    public PathBasedCacheDirective build() {
+      return new PathBasedCacheDirective(path, replication, pool);
+    }
+
+    /**
+     * Sets the path used in this request.
+     * 
+     * @param path The path used in this request.
+     * @return This builder, for call chaining.
+     */
+    public Builder setPath(Path path) {
+      this.path = path;
+      return this;
+    }
+
+    /**
+     * Sets the replication used in this request.
+     * 
+     * @param replication The replication used in this request.
+     * @return This builder, for call chaining.
+     */
+    public Builder setReplication(short replication) {
+      this.replication = replication;
+      return this;
+    }
+
+    /**
+     * Sets the pool used in this request.
+     * 
+     * @param pool The pool used in this request.
+     * @return This builder, for call chaining.
+     */
+    public Builder setPool(String pool) {
+      this.pool = pool;
+      return this;
+    }
+  }
+
+  private final Path path;
+  private final short replication;
+  private final String pool;
+
+  /**
+   * @return The path used in this request.
+   */
+  public Path getPath() {
+    return path;
+  }
+
+  /**
+   * @return The number of times the block should be cached.
+   */
+  public short getReplication() {
+    return replication;
+  }
+
+  /**
+   * @return The pool used in this request.
+   */
+  public String getPool() {
+    return pool;
+  }
+
+  /**
+   * Check if this PathBasedCacheDirective is valid.
+   * 
+   * @throws IOException
+   *     If this PathBasedCacheDirective is not valid.
+   */
+  public void validate() throws IOException {
+    if (!DFSUtil.isValidName(path.toUri().getPath())) {
+      throw new InvalidPathNameError(this);
+    }
+    if (replication <= 0) {
+      throw new IOException("Tried to request a cache replication " +
+          "factor of " + replication + ", but that is less than 1.");
+    }
+    if (pool.isEmpty()) {
+      throw new InvalidPoolNameError(this);
+    }
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    if (o == null) {
+      return false;
+    }
+    if (getClass() != o.getClass()) {
+      return false;
+    }
+    PathBasedCacheDirective other = (PathBasedCacheDirective)o;
+    return new EqualsBuilder().append(getPath(), other.getPath()).
+        append(getReplication(), other.getReplication()).
+        append(getPool(), other.getPool()).
+        isEquals();
+  }
+
+  @Override
+  public int hashCode() {
+    return new HashCodeBuilder().append(getPath()).
+        append(replication).
+        append(getPool()).
+        hashCode();
+  }
+
+  @Override
+  public String toString() {
+    StringBuilder builder = new StringBuilder();
+    builder.append("{ path:").append(path).
+      append(", replication:").append(replication).
+      append(", pool:").append(pool).
+      append(" }");
+    return builder.toString();
+  }
+
+  /**
+   * Protected constructor.  Callers use Builder to create new instances.
+   * 
+   * @param path The path used in this request.
+   * @param replication The replication used in this request.
+   * @param pool The pool used in this request.
+   */
+  protected PathBasedCacheDirective(Path path, short replication, String pool) {
+    Preconditions.checkNotNull(path);
+    Preconditions.checkNotNull(pool);
+    this.path = path;
+    this.replication = replication;
+    this.pool = pool;
+  }
+};
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/PathBasedCacheEntry.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/PathBasedCacheEntry.java
new file mode 100644
index 0000000..b07a26d
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/PathBasedCacheEntry.java
@@ -0,0 +1,98 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.protocol;
+
+import org.apache.commons.lang.builder.HashCodeBuilder;
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hdfs.server.namenode.CachePool;
+
+import com.google.common.base.Preconditions;
+
+/**
+ * Represents an entry in the PathBasedCache on the NameNode.
+ *
+ * This is an implementation class, not part of the public API.
+ */
+@InterfaceAudience.Private
+public final class PathBasedCacheEntry {
+  private final long entryId;
+  private final String path;
+  private final short replication;
+  private final CachePool pool;
+
+  public PathBasedCacheEntry(long entryId, String path,
+      short replication, CachePool pool) {
+    Preconditions.checkArgument(entryId > 0);
+    this.entryId = entryId;
+    Preconditions.checkArgument(replication > 0);
+    this.path = path;
+    Preconditions.checkNotNull(pool);
+    this.replication = replication;
+    Preconditions.checkNotNull(path);
+    this.pool = pool;
+  }
+
+  public long getEntryId() {
+    return entryId;
+  }
+
+  public String getPath() {
+    return path;
+  }
+
+  public CachePool getPool() {
+    return pool;
+  }
+
+  public short getReplication() {
+    return replication;
+  }
+
+  @Override
+  public String toString() {
+    StringBuilder builder = new StringBuilder();
+    builder.append("{ entryId:").append(entryId).
+      append(", path:").append(path).
+      append(", replication:").append(replication).
+      append(", pool:").append(pool).
+      append(" }");
+    return builder.toString();
+  }
+
+  public PathBasedCacheDescriptor getDescriptor() {
+    return new PathBasedCacheDescriptor(entryId, new Path(path), replication,
+        pool.getPoolName());
+  }
+  
+  @Override
+  public boolean equals(Object o) {
+    if (o == null) { return false; }
+    if (o == this) { return true; }
+    if (o.getClass() != this.getClass()) {
+      return false;
+    }
+    PathBasedCacheEntry other = (PathBasedCacheEntry)o;
+    return entryId == other.entryId;
+  }
+
+  @Override
+  public int hashCode() {
+    return new HashCodeBuilder().append(entryId).toHashCode();
+  }
+};
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/RemovePathBasedCacheDescriptorException.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/RemovePathBasedCacheDescriptorException.java
new file mode 100644
index 0000000..7560062
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/RemovePathBasedCacheDescriptorException.java
@@ -0,0 +1,85 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.protocol;
+
+import java.io.IOException;
+
+/**
+ * An exception which occurred when trying to remove a PathBasedCache entry.
+ */
+public abstract class RemovePathBasedCacheDescriptorException extends IOException {
+  private static final long serialVersionUID = 1L;
+
+  public RemovePathBasedCacheDescriptorException(String description) {
+    super(description);
+  }
+
+  public final static class InvalidIdException
+      extends RemovePathBasedCacheDescriptorException {
+    private static final long serialVersionUID = 1L;
+
+    public InvalidIdException(String msg) {
+      super(msg);
+    }
+
+    public InvalidIdException(long entryId) {
+      this("invalid PathBasedCacheDescriptor id " + entryId);
+    }
+  }
+
+  public final static class RemovePermissionDeniedException
+      extends RemovePathBasedCacheDescriptorException {
+    private static final long serialVersionUID = 1L;
+
+    public RemovePermissionDeniedException(String msg) {
+      super(msg);
+    }
+
+    public RemovePermissionDeniedException(long entryId) {
+      this("permission denied when trying to remove " + 
+          "PathBasedCacheDescriptor id " + entryId);
+    }
+  }
+
+  public final static class NoSuchIdException
+      extends RemovePathBasedCacheDescriptorException {
+    private static final long serialVersionUID = 1L;
+
+    public NoSuchIdException(String msg) {
+      super(msg);
+    }
+
+    public NoSuchIdException(long entryId) {
+      this("there is no PathBasedCacheDescriptor with id " + entryId);
+    }
+  }
+
+  public final static class UnexpectedRemovePathBasedCacheDescriptorException
+      extends RemovePathBasedCacheDescriptorException {
+    private static final long serialVersionUID = 1L;
+
+    public UnexpectedRemovePathBasedCacheDescriptorException(String msg) {
+      super(msg);
+    }
+
+    public UnexpectedRemovePathBasedCacheDescriptorException(long id) {
+      this("encountered an unexpected error when trying to " +
+          "remove PathBasedCacheDescriptor with id " + id);
+    }
+  }
+}
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/RemovePathBasedCacheEntryException.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/RemovePathBasedCacheEntryException.java
new file mode 100644
index 0000000..e657d41
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocol/RemovePathBasedCacheEntryException.java
@@ -0,0 +1,78 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.protocol;
+
+import java.io.IOException;
+
+import com.google.common.base.Preconditions;
+
+/**
+ * An exception which occurred when trying to remove a PathBasedCache entry.
+ */
+public abstract class RemovePathBasedCacheEntryException extends IOException {
+  private static final long serialVersionUID = 1L;
+
+  private final long entryId;
+
+  public RemovePathBasedCacheEntryException(String description, long entryId) {
+    super(description);
+    this.entryId = entryId;
+  }
+    
+  public long getEntryId() {
+    return this.entryId;
+  }
+
+  public final static class InvalidIdException
+      extends RemovePathBasedCacheEntryException {
+    private static final long serialVersionUID = 1L;
+
+    public InvalidIdException(long entryId) {
+      super("invalid cache path entry id " + entryId, entryId);
+    }
+  }
+
+  public final static class RemovePermissionDeniedException
+      extends RemovePathBasedCacheEntryException {
+    private static final long serialVersionUID = 1L;
+
+    public RemovePermissionDeniedException(long entryId) {
+      super("permission denied when trying to remove PathBasedCache entry id " +
+        entryId, entryId);
+    }
+  }
+
+  public final static class NoSuchIdException
+      extends RemovePathBasedCacheEntryException {
+    private static final long serialVersionUID = 1L;
+
+    public NoSuchIdException(long entryId) {
+      super("there is no PathBasedCache entry with id " + entryId, entryId);
+    }
+  }
+
+  public final static class UnexpectedRemovePathBasedCacheEntryException
+      extends RemovePathBasedCacheEntryException {
+    private static final long serialVersionUID = 1L;
+
+    public UnexpectedRemovePathBasedCacheEntryException(long id) {
+      super("encountered an unexpected error when trying to " +
+          "remove PathBasedCache entry id " + id, id);
+    }
+  }
+}
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientNamenodeProtocolServerSideTranslatorPB.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientNamenodeProtocolServerSideTranslatorPB.java
index d7a18a6..5cc3443 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientNamenodeProtocolServerSideTranslatorPB.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientNamenodeProtocolServerSideTranslatorPB.java
@@ -25,18 +25,32 @@
 import org.apache.hadoop.fs.ContentSummary;
 import org.apache.hadoop.fs.FsServerDefaults;
 import org.apache.hadoop.fs.Options.Rename;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.fs.RemoteIterator;
+import org.apache.hadoop.fs.permission.FsPermission;
+import org.apache.hadoop.hdfs.protocol.AddPathBasedCacheDirectiveException.EmptyPathError;
+import org.apache.hadoop.hdfs.protocol.CachePoolInfo;
 import org.apache.hadoop.hdfs.protocol.ClientProtocol;
 import org.apache.hadoop.hdfs.protocol.CorruptFileBlocks;
 import org.apache.hadoop.hdfs.protocol.DirectoryListing;
 import org.apache.hadoop.hdfs.protocol.HdfsFileStatus;
 import org.apache.hadoop.hdfs.protocol.LocatedBlock;
 import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDescriptor;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDirective;
+import org.apache.hadoop.hdfs.protocol.RemovePathBasedCacheDescriptorException.InvalidIdException;
+import org.apache.hadoop.hdfs.protocol.RemovePathBasedCacheDescriptorException.NoSuchIdException;
+import org.apache.hadoop.hdfs.protocol.RemovePathBasedCacheDescriptorException.RemovePermissionDeniedException;
 import org.apache.hadoop.hdfs.protocol.SnapshotDiffReport;
 import org.apache.hadoop.hdfs.protocol.SnapshottableDirectoryStatus;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AbandonBlockRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AbandonBlockResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AddBlockRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AddBlockResponseProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AddCachePoolRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AddCachePoolResponseProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AddPathBasedCacheDirectiveRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AddPathBasedCacheDirectiveResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AllowSnapshotRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AllowSnapshotResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AppendRequestProto;
@@ -92,16 +106,29 @@
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetSnapshottableDirListingResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.IsFileClosedRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.IsFileClosedResponseProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ListCachePoolsRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ListCachePoolsResponseElementProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ListCachePoolsResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ListCorruptFileBlocksRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ListCorruptFileBlocksResponseProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ListPathBasedCacheDescriptorsElementProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ListPathBasedCacheDescriptorsRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ListPathBasedCacheDescriptorsResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.MetaSaveRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.MetaSaveResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.MkdirsRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.MkdirsResponseProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ModifyCachePoolRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ModifyCachePoolResponseProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.PathBasedCacheDirectiveProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.RecoverLeaseRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.RecoverLeaseResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.RefreshNodesRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.RefreshNodesResponseProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.RemoveCachePoolRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.RemoveCachePoolResponseProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.RemovePathBasedCacheDescriptorRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.RemovePathBasedCacheDescriptorResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.Rename2RequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.Rename2ResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.RenameRequestProto;
@@ -151,6 +178,9 @@
 import org.apache.hadoop.security.proto.SecurityProtos.RenewDelegationTokenResponseProto;
 import org.apache.hadoop.security.token.Token;
 
+import org.apache.commons.lang.StringUtils;
+
+import com.google.common.primitives.Shorts;
 import com.google.protobuf.RpcController;
 import com.google.protobuf.ServiceException;
 
@@ -1003,5 +1033,183 @@
       throw new ServiceException(e);
     }
   }
+
+  @Override
+  public AddPathBasedCacheDirectiveResponseProto addPathBasedCacheDirective(
+      RpcController controller, AddPathBasedCacheDirectiveRequestProto request)
+      throws ServiceException {
+    try {
+      PathBasedCacheDirectiveProto proto = request.getDirective();
+      if (StringUtils.isEmpty(proto.getPath())) {
+        throw new EmptyPathError();
+      }
+      PathBasedCacheDirective directive = new PathBasedCacheDirective.Builder().
+          setPath(new Path(proto.getPath())).
+          setReplication(Shorts.checkedCast(proto.getReplication())).
+          setPool(proto.getPool()).
+          build();
+      PathBasedCacheDescriptor descriptor =
+          server.addPathBasedCacheDirective(directive);
+      AddPathBasedCacheDirectiveResponseProto.Builder builder =
+         AddPathBasedCacheDirectiveResponseProto.newBuilder();
+      builder.setDescriptorId(descriptor.getEntryId());
+      return builder.build();
+    } catch (IOException e) {
+      throw new ServiceException(e);
+    }
+  }
+
+  @Override
+  public RemovePathBasedCacheDescriptorResponseProto removePathBasedCacheDescriptor(
+      RpcController controller,
+      RemovePathBasedCacheDescriptorRequestProto request)
+      throws ServiceException {
+    try {
+      server.removePathBasedCacheDescriptor(request.getDescriptorId());
+      RemovePathBasedCacheDescriptorResponseProto.Builder builder =
+         RemovePathBasedCacheDescriptorResponseProto.newBuilder();
+      return builder.build();
+    } catch (IOException e) {
+      throw new ServiceException(e);
+    }
+  }
+
+  @Override
+  public ListPathBasedCacheDescriptorsResponseProto listPathBasedCacheDescriptors(
+      RpcController controller, ListPathBasedCacheDescriptorsRequestProto request)
+          throws ServiceException {
+    try {
+      RemoteIterator<PathBasedCacheDescriptor> iter =
+         server.listPathBasedCacheDescriptors(request.getPrevId(),
+             request.hasPool() ? request.getPool() : null,
+             request.hasPath() ? request.getPath() : null);
+      ListPathBasedCacheDescriptorsResponseProto.Builder builder =
+          ListPathBasedCacheDescriptorsResponseProto.newBuilder();
+      long prevId = 0;
+      while (iter.hasNext()) {
+        PathBasedCacheDescriptor directive = iter.next();
+        builder.addElements(
+            ListPathBasedCacheDescriptorsElementProto.newBuilder().
+              setId(directive.getEntryId()).
+              setPath(directive.getPath().toUri().getPath()).
+              setReplication(directive.getReplication()).
+              setPool(directive.getPool()));
+        prevId = directive.getEntryId();
+      }
+      if (prevId == 0) {
+        builder.setHasMore(false);
+      } else {
+        iter = server.listPathBasedCacheDescriptors(prevId, 
+            request.hasPool() ? request.getPool() : null,
+            request.hasPath() ? request.getPath() : null);
+        builder.setHasMore(iter.hasNext());
+      }
+      return builder.build();
+    } catch (IOException e) {
+      throw new ServiceException(e);
+    }
+  }
+
+  @Override
+  public AddCachePoolResponseProto addCachePool(RpcController controller,
+      AddCachePoolRequestProto request) throws ServiceException {
+    try {
+      CachePoolInfo info =
+          new CachePoolInfo(request.getPoolName());
+      if (request.hasOwnerName()) {
+        info.setOwnerName(request.getOwnerName());
+      }
+      if (request.hasGroupName()) {
+        info.setGroupName(request.getGroupName());
+      }
+      if (request.hasMode()) {
+        info.setMode(new FsPermission((short)request.getMode()));
+      }
+      if (request.hasWeight()) {
+        info.setWeight(request.getWeight());
+      }
+      server.addCachePool(info);
+      return AddCachePoolResponseProto.newBuilder().build();
+    } catch (IOException e) {
+      throw new ServiceException(e);
+    }
+  }
   
+  @Override
+  public ModifyCachePoolResponseProto modifyCachePool(RpcController controller,
+      ModifyCachePoolRequestProto request) throws ServiceException {
+    try {
+      CachePoolInfo info =
+          new CachePoolInfo(request.getPoolName());
+      if (request.hasOwnerName()) {
+        info.setOwnerName(request.getOwnerName());
+      }
+      if (request.hasGroupName()) {
+        info.setGroupName(request.getGroupName());
+      }
+      if (request.hasMode()) {
+        info.setMode(new FsPermission((short)request.getMode()));
+      }
+      if (request.hasWeight()) {
+        info.setWeight(request.getWeight());
+      }
+      server.modifyCachePool(info);
+      return ModifyCachePoolResponseProto.newBuilder().build();
+    } catch (IOException e) {
+      throw new ServiceException(e);
+    }
+  }
+
+  @Override
+  public RemoveCachePoolResponseProto removeCachePool(RpcController controller,
+      RemoveCachePoolRequestProto request) throws ServiceException {
+    try {
+      server.removeCachePool(request.getPoolName());
+      return RemoveCachePoolResponseProto.newBuilder().build();
+    } catch (IOException e) {
+      throw new ServiceException(e);
+    }
+  }
+
+  @Override
+  public ListCachePoolsResponseProto listCachePools(RpcController controller,
+      ListCachePoolsRequestProto request) throws ServiceException {
+    try {
+      RemoteIterator<CachePoolInfo> iter =
+        server.listCachePools(request.getPrevPoolName());
+      ListCachePoolsResponseProto.Builder responseBuilder =
+        ListCachePoolsResponseProto.newBuilder();
+      String prevPoolName = null;
+      while (iter.hasNext()) {
+        CachePoolInfo pool = iter.next();
+        ListCachePoolsResponseElementProto.Builder elemBuilder = 
+            ListCachePoolsResponseElementProto.newBuilder();
+        elemBuilder.setPoolName(pool.getPoolName());
+        if (pool.getOwnerName() != null) {
+          elemBuilder.setOwnerName(pool.getOwnerName());
+        }
+        if (pool.getGroupName() != null) {
+          elemBuilder.setGroupName(pool.getGroupName());
+        }
+        if (pool.getMode() != null) {
+          elemBuilder.setMode(pool.getMode().toShort());
+        }
+        if (pool.getWeight() != null) {
+          elemBuilder.setWeight(pool.getWeight());
+        }
+        responseBuilder.addElements(elemBuilder.build());
+        prevPoolName = pool.getPoolName();
+      }
+      // fill in hasNext
+      if (prevPoolName == null) {
+        responseBuilder.setHasMore(false);
+      } else {
+        iter = server.listCachePools(prevPoolName);
+        responseBuilder.setHasMore(iter.hasNext());
+      }
+      return responseBuilder.build();
+    } catch (IOException e) {
+      throw new ServiceException(e);
+    }
+  }
 }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientNamenodeProtocolTranslatorPB.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientNamenodeProtocolTranslatorPB.java
index b5be61a..e37b8af 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientNamenodeProtocolTranslatorPB.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientNamenodeProtocolTranslatorPB.java
@@ -24,15 +24,20 @@
 
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
+import org.apache.hadoop.fs.BatchedRemoteIterator;
+import org.apache.hadoop.fs.BatchedRemoteIterator.BatchedEntries;
 import org.apache.hadoop.fs.ContentSummary;
 import org.apache.hadoop.fs.CreateFlag;
 import org.apache.hadoop.fs.FileAlreadyExistsException;
 import org.apache.hadoop.fs.FsServerDefaults;
 import org.apache.hadoop.fs.Options.Rename;
 import org.apache.hadoop.fs.ParentNotDirectoryException;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.fs.RemoteIterator;
 import org.apache.hadoop.fs.UnresolvedLinkException;
 import org.apache.hadoop.fs.permission.FsPermission;
 import org.apache.hadoop.hdfs.protocol.AlreadyBeingCreatedException;
+import org.apache.hadoop.hdfs.protocol.CachePoolInfo;
 import org.apache.hadoop.hdfs.protocol.ClientProtocol;
 import org.apache.hadoop.hdfs.protocol.CorruptFileBlocks;
 import org.apache.hadoop.hdfs.protocol.DSQuotaExceededException;
@@ -46,10 +51,15 @@
 import org.apache.hadoop.hdfs.protocol.LocatedBlock;
 import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
 import org.apache.hadoop.hdfs.protocol.NSQuotaExceededException;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDescriptor;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDirective;
 import org.apache.hadoop.hdfs.protocol.SnapshotDiffReport;
 import org.apache.hadoop.hdfs.protocol.SnapshottableDirectoryStatus;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AbandonBlockRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AddBlockRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AddCachePoolRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AddPathBasedCacheDirectiveRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AddPathBasedCacheDirectiveResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AllowSnapshotRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AppendRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AppendResponseProto;
@@ -87,11 +97,21 @@
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetSnapshottableDirListingRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetSnapshottableDirListingResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.IsFileClosedRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ListCachePoolsRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ListCachePoolsResponseElementProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ListCachePoolsResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ListCorruptFileBlocksRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ListPathBasedCacheDescriptorsElementProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ListPathBasedCacheDescriptorsRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ListPathBasedCacheDescriptorsResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.MetaSaveRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.MkdirsRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ModifyCachePoolRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.PathBasedCacheDirectiveProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.RecoverLeaseRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.RefreshNodesRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.RemoveCachePoolRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.RemovePathBasedCacheDescriptorRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.Rename2RequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.RenameRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.RenameSnapshotRequestProto;
@@ -128,6 +148,7 @@
 import org.apache.hadoop.security.proto.SecurityProtos.RenewDelegationTokenRequestProto;
 import org.apache.hadoop.security.token.Token;
 
+import com.google.common.primitives.Shorts;
 import com.google.protobuf.ByteString;
 import com.google.protobuf.ServiceException;
 
@@ -982,4 +1003,231 @@
       throw ProtobufHelper.getRemoteException(e);
     }
   }
+
+  @Override
+  public PathBasedCacheDescriptor addPathBasedCacheDirective(
+      PathBasedCacheDirective directive) throws IOException {
+    try {
+      AddPathBasedCacheDirectiveRequestProto.Builder builder =
+          AddPathBasedCacheDirectiveRequestProto.newBuilder();
+      builder.setDirective(PathBasedCacheDirectiveProto.newBuilder()
+          .setPath(directive.getPath().toUri().getPath())
+          .setReplication(directive.getReplication())
+          .setPool(directive.getPool())
+          .build());
+      AddPathBasedCacheDirectiveResponseProto result = 
+          rpcProxy.addPathBasedCacheDirective(null, builder.build());
+      return new PathBasedCacheDescriptor(result.getDescriptorId(),
+          directive.getPath(), directive.getReplication(),
+          directive.getPool());
+    } catch (ServiceException e) {
+      throw ProtobufHelper.getRemoteException(e);
+    }
+  }
+
+  @Override
+  public void removePathBasedCacheDescriptor(Long id)
+      throws IOException {
+    try {
+      RemovePathBasedCacheDescriptorRequestProto.Builder builder =
+          RemovePathBasedCacheDescriptorRequestProto.newBuilder();
+      builder.setDescriptorId(id);
+      rpcProxy.removePathBasedCacheDescriptor(null, builder.build());
+    } catch (ServiceException e) {
+      throw ProtobufHelper.getRemoteException(e);
+    }
+  }
+
+  private static class BatchedPathBasedCacheEntries
+      implements BatchedEntries<PathBasedCacheDescriptor> {
+    private ListPathBasedCacheDescriptorsResponseProto response;
+
+    BatchedPathBasedCacheEntries(ListPathBasedCacheDescriptorsResponseProto response) {
+      this.response = response;
+    }
+
+    @Override
+    public PathBasedCacheDescriptor get(int i) {
+      ListPathBasedCacheDescriptorsElementProto elementProto =
+        response.getElements(i);
+      return new PathBasedCacheDescriptor(elementProto.getId(),
+          new Path(elementProto.getPath()),
+          Shorts.checkedCast(elementProto.getReplication()),
+          elementProto.getPool());
+    }
+
+    @Override
+    public int size() {
+      return response.getElementsCount();
+    }
+    
+    @Override
+    public boolean hasMore() {
+      return response.getHasMore();
+    }
+  }
+
+  private class PathBasedCacheEntriesIterator
+      extends BatchedRemoteIterator<Long, PathBasedCacheDescriptor> {
+    private final String pool;
+    private final String path;
+
+    public PathBasedCacheEntriesIterator(long prevKey, String pool, String path) {
+      super(prevKey);
+      this.pool = pool;
+      this.path = path;
+    }
+
+    @Override
+    public BatchedEntries<PathBasedCacheDescriptor> makeRequest(
+        Long nextKey) throws IOException {
+      ListPathBasedCacheDescriptorsResponseProto response;
+      try {
+        ListPathBasedCacheDescriptorsRequestProto.Builder builder =
+            ListPathBasedCacheDescriptorsRequestProto.newBuilder().setPrevId(nextKey);
+        if (pool != null) {
+          builder.setPool(pool);
+        }
+        if (path != null) {
+          builder.setPath(path);
+        }
+        ListPathBasedCacheDescriptorsRequestProto req = builder.build();
+        response = rpcProxy.listPathBasedCacheDescriptors(null, req);
+      } catch (ServiceException e) {
+        throw ProtobufHelper.getRemoteException(e);
+      }
+      return new BatchedPathBasedCacheEntries(response);
+    }
+
+    @Override
+    public Long elementToPrevKey(PathBasedCacheDescriptor element) {
+      return element.getEntryId();
+    }
+  }
+
+  @Override
+  public RemoteIterator<PathBasedCacheDescriptor> listPathBasedCacheDescriptors(long prevId,
+      String pool, String path) throws IOException {
+    return new PathBasedCacheEntriesIterator(prevId, pool, path);
+  }
+
+  @Override
+  public void addCachePool(CachePoolInfo info) throws IOException {
+    AddCachePoolRequestProto.Builder builder = 
+        AddCachePoolRequestProto.newBuilder();
+    builder.setPoolName(info.getPoolName());
+    if (info.getOwnerName() != null) {
+      builder.setOwnerName(info.getOwnerName());
+    }
+    if (info.getGroupName() != null) {
+      builder.setGroupName(info.getGroupName());
+    }
+    if (info.getMode() != null) {
+      builder.setMode(info.getMode().toShort());
+    }
+    if (info.getWeight() != null) {
+      builder.setWeight(info.getWeight());
+    }
+    try {
+      rpcProxy.addCachePool(null, builder.build());
+    } catch (ServiceException e) {
+      throw ProtobufHelper.getRemoteException(e);
+    }
+  }
+
+  @Override
+  public void modifyCachePool(CachePoolInfo req) throws IOException {
+    ModifyCachePoolRequestProto.Builder builder = 
+        ModifyCachePoolRequestProto.newBuilder();
+    builder.setPoolName(req.getPoolName());
+    if (req.getOwnerName() != null) {
+      builder.setOwnerName(req.getOwnerName());
+    }
+    if (req.getGroupName() != null) {
+      builder.setGroupName(req.getGroupName());
+    }
+    if (req.getMode() != null) {
+      builder.setMode(req.getMode().toShort());
+    }
+    if (req.getWeight() != null) {
+      builder.setWeight(req.getWeight());
+    }
+    try {
+      rpcProxy.modifyCachePool(null, builder.build());
+    } catch (ServiceException e) {
+      throw ProtobufHelper.getRemoteException(e);
+    }
+  }
+
+  @Override
+  public void removeCachePool(String cachePoolName) throws IOException {
+    try {
+      rpcProxy.removeCachePool(null, 
+          RemoveCachePoolRequestProto.newBuilder().
+            setPoolName(cachePoolName).build());
+    } catch (ServiceException e) {
+      throw ProtobufHelper.getRemoteException(e);
+    }
+  }
+
+  private static class BatchedPathDirectiveEntries
+      implements BatchedEntries<CachePoolInfo> {
+    private final ListCachePoolsResponseProto proto;
+    
+    public BatchedPathDirectiveEntries(ListCachePoolsResponseProto proto) {
+      this.proto = proto;
+    }
+      
+    @Override
+    public CachePoolInfo get(int i) {
+      ListCachePoolsResponseElementProto elem = proto.getElements(i);
+      return new CachePoolInfo(elem.getPoolName()).
+          setOwnerName(elem.getOwnerName()).
+          setGroupName(elem.getGroupName()).
+          setMode(new FsPermission((short)elem.getMode())).
+          setWeight(elem.getWeight());
+    }
+
+    @Override
+    public int size() {
+      return proto.getElementsCount();
+    }
+    
+    @Override
+    public boolean hasMore() {
+      return proto.getHasMore();
+    }
+  }
+  
+  private class CachePoolIterator 
+      extends BatchedRemoteIterator<String, CachePoolInfo> {
+
+    public CachePoolIterator(String prevKey) {
+      super(prevKey);
+    }
+
+    @Override
+    public BatchedEntries<CachePoolInfo> makeRequest(String prevKey)
+        throws IOException {
+      try {
+        return new BatchedPathDirectiveEntries(
+            rpcProxy.listCachePools(null, 
+              ListCachePoolsRequestProto.newBuilder().
+                setPrevPoolName(prevKey).build()));
+      } catch (ServiceException e) {
+        throw ProtobufHelper.getRemoteException(e);
+      }
+    }
+
+    @Override
+    public String elementToPrevKey(CachePoolInfo element) {
+      return element.getPoolName();
+    }
+  }
+
+  @Override
+  public RemoteIterator<CachePoolInfo> listCachePools(String prevKey)
+      throws IOException {
+    return new CachePoolIterator(prevKey);
+  }
 }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/DatanodeProtocolClientSideTranslatorPB.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/DatanodeProtocolClientSideTranslatorPB.java
index fd4cc4b..f12a92f 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/DatanodeProtocolClientSideTranslatorPB.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/DatanodeProtocolClientSideTranslatorPB.java
@@ -22,6 +22,7 @@
 import java.io.IOException;
 import java.net.InetSocketAddress;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 import java.util.concurrent.TimeUnit;
 
@@ -36,6 +37,8 @@
 import org.apache.hadoop.hdfs.protocol.proto.DatanodeProtocolProtos.BlockReceivedAndDeletedRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.DatanodeProtocolProtos.BlockReportRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.DatanodeProtocolProtos.BlockReportResponseProto;
+import org.apache.hadoop.hdfs.protocol.proto.DatanodeProtocolProtos.CacheReportRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.DatanodeProtocolProtos.CacheReportResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.DatanodeProtocolProtos.CommitBlockSynchronizationRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.DatanodeProtocolProtos.DatanodeCommandProto;
 import org.apache.hadoop.hdfs.protocol.proto.DatanodeProtocolProtos.ErrorReportRequestProto;
@@ -152,8 +155,9 @@
 
   @Override
   public HeartbeatResponse sendHeartbeat(DatanodeRegistration registration,
-      StorageReport[] reports, int xmitsInProgress, int xceiverCount,
-      int failedVolumes) throws IOException {
+      StorageReport[] reports, long dnCacheCapacity, long dnCacheUsed,
+          int xmitsInProgress, int xceiverCount, int failedVolumes)
+              throws IOException {
     HeartbeatRequestProto.Builder builder = HeartbeatRequestProto.newBuilder()
         .setRegistration(PBHelper.convert(registration))
         .setXmitsInProgress(xmitsInProgress).setXceiverCount(xceiverCount)
@@ -161,7 +165,12 @@
     for (StorageReport r : reports) {
       builder.addReports(PBHelper.convert(r));
     }
-    
+    if (dnCacheCapacity != 0) {
+      builder.setDnCacheCapacity(dnCacheCapacity);
+    }
+    if (dnCacheUsed != 0) {
+      builder.setDnCacheUsed(dnCacheUsed);
+    }
     HeartbeatResponseProto resp;
     try {
       resp = rpcProxy.sendHeartbeat(NULL_CONTROLLER, builder.build());
@@ -203,6 +212,29 @@
   }
 
   @Override
+  public DatanodeCommand cacheReport(DatanodeRegistration registration,
+      String poolId, List<Long> blockIds) throws IOException {
+    CacheReportRequestProto.Builder builder =
+        CacheReportRequestProto.newBuilder()
+        .setRegistration(PBHelper.convert(registration))
+        .setBlockPoolId(poolId);
+    for (Long blockId : blockIds) {
+      builder.addBlocks(blockId);
+    }
+    
+    CacheReportResponseProto resp;
+    try {
+      resp = rpcProxy.cacheReport(NULL_CONTROLLER, builder.build());
+    } catch (ServiceException se) {
+      throw ProtobufHelper.getRemoteException(se);
+    }
+    if (resp.hasCmd()) {
+      return PBHelper.convert(resp.getCmd());
+    }
+    return null;
+  }
+
+  @Override
   public void blockReceivedAndDeleted(DatanodeRegistration registration,
       String poolId, StorageReceivedDeletedBlocks[] receivedAndDeletedBlocks)
       throws IOException {
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/DatanodeProtocolServerSideTranslatorPB.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/DatanodeProtocolServerSideTranslatorPB.java
index 3e42460..ab06770 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/DatanodeProtocolServerSideTranslatorPB.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/DatanodeProtocolServerSideTranslatorPB.java
@@ -27,6 +27,8 @@
 import org.apache.hadoop.hdfs.protocol.proto.DatanodeProtocolProtos.BlockReceivedAndDeletedResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.DatanodeProtocolProtos.BlockReportRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.DatanodeProtocolProtos.BlockReportResponseProto;
+import org.apache.hadoop.hdfs.protocol.proto.DatanodeProtocolProtos.CacheReportRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.DatanodeProtocolProtos.CacheReportResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.DatanodeProtocolProtos.CommitBlockSynchronizationRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.DatanodeProtocolProtos.CommitBlockSynchronizationResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.DatanodeProtocolProtos.ErrorReportRequestProto;
@@ -55,6 +57,7 @@
 import org.apache.hadoop.hdfs.server.protocol.StorageReceivedDeletedBlocks;
 import org.apache.hadoop.hdfs.server.protocol.StorageReport;
 
+import com.google.common.primitives.Longs;
 import com.google.protobuf.RpcController;
 import com.google.protobuf.ServiceException;
 
@@ -109,8 +112,9 @@
             p.getBlockPoolUsed());
       }
       response = impl.sendHeartbeat(PBHelper.convert(request.getRegistration()),
-          report, request.getXmitsInProgress(), request.getXceiverCount(),
-          request.getFailedVolumes());
+          report, request.getDnCacheCapacity(), request.getDnCacheUsed(),
+          request.getXmitsInProgress(),
+          request.getXceiverCount(), request.getFailedVolumes());
     } catch (IOException e) {
       throw new ServiceException(e);
     }
@@ -160,6 +164,27 @@
   }
 
   @Override
+  public CacheReportResponseProto cacheReport(RpcController controller,
+      CacheReportRequestProto request) throws ServiceException {
+    DatanodeCommand cmd = null;
+    try {
+      cmd = impl.cacheReport(
+          PBHelper.convert(request.getRegistration()),
+          request.getBlockPoolId(),
+          request.getBlocksList());
+    } catch (IOException e) {
+      throw new ServiceException(e);
+    }
+    CacheReportResponseProto.Builder builder =
+        CacheReportResponseProto.newBuilder();
+    if (cmd != null) {
+      builder.setCmd(PBHelper.convert(cmd));
+    }
+    return builder.build();
+  }
+
+
+  @Override
   public BlockReceivedAndDeletedResponseProto blockReceivedAndDeleted(
       RpcController controller, BlockReceivedAndDeletedRequestProto request)
       throws ServiceException {
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/PBHelper.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/PBHelper.java
index 18a689f..4626dc0 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/PBHelper.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/PBHelper.java
@@ -57,6 +57,7 @@
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.SafeModeActionProto;
 import org.apache.hadoop.hdfs.protocol.proto.DatanodeProtocolProtos.BalancerBandwidthCommandProto;
 import org.apache.hadoop.hdfs.protocol.proto.DatanodeProtocolProtos.BlockCommandProto;
+import org.apache.hadoop.hdfs.protocol.proto.DatanodeProtocolProtos.BlockIdCommandProto;
 import org.apache.hadoop.hdfs.protocol.proto.DatanodeProtocolProtos.BlockRecoveryCommandProto;
 import org.apache.hadoop.hdfs.protocol.proto.DatanodeProtocolProtos.DatanodeCommandProto;
 import org.apache.hadoop.hdfs.protocol.proto.DatanodeProtocolProtos.DatanodeRegistrationProto;
@@ -118,6 +119,7 @@
 import org.apache.hadoop.hdfs.server.namenode.INodeId;
 import org.apache.hadoop.hdfs.server.protocol.BalancerBandwidthCommand;
 import org.apache.hadoop.hdfs.server.protocol.BlockCommand;
+import org.apache.hadoop.hdfs.server.protocol.BlockIdCommand;
 import org.apache.hadoop.hdfs.server.protocol.BlockRecoveryCommand;
 import org.apache.hadoop.hdfs.server.protocol.BlockRecoveryCommand.RecoveringBlock;
 import org.apache.hadoop.hdfs.server.protocol.BlocksWithLocations;
@@ -148,6 +150,7 @@
 import org.apache.hadoop.security.token.Token;
 import org.apache.hadoop.util.DataChecksum;
 
+import com.google.common.base.Preconditions;
 import com.google.common.collect.Lists;
 import com.google.protobuf.ByteString;
 import com.google.protobuf.CodedInputStream;
@@ -472,7 +475,8 @@
         PBHelper.convert(di.getId()),
         di.hasLocation() ? di.getLocation() : null , 
         di.getCapacity(),  di.getDfsUsed(),  di.getRemaining(),
-        di.getBlockPoolUsed()  ,  di.getLastUpdate() , di.getXceiverCount() ,
+        di.getBlockPoolUsed(), di.getCacheCapacity(), di.getCacheUsed(),
+        di.getLastUpdate(), di.getXceiverCount(),
         PBHelper.convert(di.getAdminState())); 
   }
   
@@ -565,9 +569,21 @@
     if (b == null) return null;
     Builder builder = LocatedBlockProto.newBuilder();
     DatanodeInfo[] locs = b.getLocations();
+    List<DatanodeInfo> cachedLocs =
+        Lists.newLinkedList(Arrays.asList(b.getCachedLocations()));
     for (int i = 0; i < locs.length; i++) {
-      builder.addLocs(i, PBHelper.convert(locs[i]));
+      DatanodeInfo loc = locs[i];
+      builder.addLocs(i, PBHelper.convert(loc));
+      boolean locIsCached = cachedLocs.contains(loc);
+      builder.addIsCached(locIsCached);
+      if (locIsCached) {
+        cachedLocs.remove(loc);
+      }
     }
+    Preconditions.checkArgument(cachedLocs.size() == 0,
+        "Found additional cached replica locations that are not in the set of"
+        + " storage-backed locations!");
+
     return builder.setB(PBHelper.convert(b.getBlock()))
         .setBlockToken(PBHelper.convert(b.getBlockToken()))
         .setCorrupt(b.isCorrupt()).setOffset(b.getStartOffset()).build();
@@ -580,9 +596,20 @@
     for (int i = 0; i < locs.size(); i++) {
       targets[i] = PBHelper.convert(locs.get(i));
     }
+    // Set values from the isCached list, re-using references from loc
+    List<DatanodeInfo> cachedLocs = new ArrayList<DatanodeInfo>(locs.size());
+    List<Boolean> isCachedList = proto.getIsCachedList();
+    for (int i=0; i<isCachedList.size(); i++) {
+      if (isCachedList.get(i)) {
+        cachedLocs.add(targets[i]);
+      }
+    }
+
     LocatedBlock lb = new LocatedBlock(PBHelper.convert(proto.getB()), targets,
-        proto.getOffset(), proto.getCorrupt());
+        proto.getOffset(), proto.getCorrupt(),
+        cachedLocs.toArray(new DatanodeInfo[0]));
     lb.setBlockToken(PBHelper.convert(proto.getBlockToken()));
+
     return lb;
   }
 
@@ -671,6 +698,8 @@
       return PBHelper.convert(proto.getKeyUpdateCmd());
     case RegisterCommand:
       return REG_CMD;
+    case BlockIdCommand:
+      return PBHelper.convert(proto.getBlkIdCmd());
     }
     return null;
   }
@@ -723,6 +752,26 @@
     builder.addAllTargets(PBHelper.convert(cmd.getTargets()));
     return builder.build();
   }
+  
+  public static BlockIdCommandProto convert(BlockIdCommand cmd) {
+    BlockIdCommandProto.Builder builder = BlockIdCommandProto.newBuilder()
+        .setBlockPoolId(cmd.getBlockPoolId());
+    switch (cmd.getAction()) {
+    case DatanodeProtocol.DNA_CACHE:
+      builder.setAction(BlockIdCommandProto.Action.CACHE);
+      break;
+    case DatanodeProtocol.DNA_UNCACHE:
+      builder.setAction(BlockIdCommandProto.Action.UNCACHE);
+      break;
+    default:
+      throw new AssertionError("Invalid action");
+    }
+    long[] blockIds = cmd.getBlockIds();
+    for (int i = 0; i < blockIds.length; i++) {
+      builder.addBlockIds(blockIds[i]);
+    }
+    return builder.build();
+  }
 
   private static List<DatanodeInfosProto> convert(DatanodeInfo[][] targets) {
     DatanodeInfosProto[] ret = new DatanodeInfosProto[targets.length];
@@ -766,8 +815,13 @@
     case DatanodeProtocol.DNA_TRANSFER:
     case DatanodeProtocol.DNA_INVALIDATE:
     case DatanodeProtocol.DNA_SHUTDOWN:
-      builder.setCmdType(DatanodeCommandProto.Type.BlockCommand).setBlkCmd(
-          PBHelper.convert((BlockCommand) datanodeCommand));
+      builder.setCmdType(DatanodeCommandProto.Type.BlockCommand).
+        setBlkCmd(PBHelper.convert((BlockCommand) datanodeCommand));
+      break;
+    case DatanodeProtocol.DNA_CACHE:
+    case DatanodeProtocol.DNA_UNCACHE:
+      builder.setCmdType(DatanodeCommandProto.Type.BlockIdCommand).
+        setBlkIdCmd(PBHelper.convert((BlockIdCommand) datanodeCommand));
       break;
     case DatanodeProtocol.DNA_UNKNOWN: //Not expected
     default:
@@ -818,10 +872,32 @@
     case SHUTDOWN:
       action = DatanodeProtocol.DNA_SHUTDOWN;
       break;
+    default:
+      throw new AssertionError("Unknown action type: " + blkCmd.getAction());
     }
     return new BlockCommand(action, blkCmd.getBlockPoolId(), blocks, targets);
   }
 
+  public static BlockIdCommand convert(BlockIdCommandProto blkIdCmd) {
+    int numBlockIds = blkIdCmd.getBlockIdsCount();
+    long blockIds[] = new long[numBlockIds];
+    for (int i = 0; i < numBlockIds; i++) {
+      blockIds[i] = blkIdCmd.getBlockIds(i);
+    }
+    int action = DatanodeProtocol.DNA_UNKNOWN;
+    switch (blkIdCmd.getAction()) {
+    case CACHE:
+      action = DatanodeProtocol.DNA_CACHE;
+      break;
+    case UNCACHE:
+      action = DatanodeProtocol.DNA_UNCACHE;
+      break;
+    default:
+      throw new AssertionError("Unknown action type: " + blkIdCmd.getAction());
+    }
+    return new BlockIdCommand(action, blkIdCmd.getBlockPoolId(), blockIds);
+  }
+
   public static DatanodeInfo[] convert(DatanodeInfosProto datanodeInfosProto) {
     List<DatanodeInfoProto> proto = datanodeInfosProto.getDatanodesList();
     DatanodeInfo[] infos = new DatanodeInfo[proto.size()];
@@ -1358,10 +1434,11 @@
   }
 
   public static StorageReportProto convert(StorageReport r) {
-    return StorageReportProto.newBuilder()
+    StorageReportProto.Builder builder = StorageReportProto.newBuilder()
         .setBlockPoolUsed(r.getBlockPoolUsed()).setCapacity(r.getCapacity())
         .setDfsUsed(r.getDfsUsed()).setRemaining(r.getRemaining())
-        .setStorageID(r.getStorageID()).build();
+        .setStorageID(r.getStorageID());
+    return builder.build();
   }
 
   public static JournalInfo convert(JournalInfoProto info) {
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockInfo.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockInfo.java
index 8307180..7376f00b 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockInfo.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockInfo.java
@@ -85,7 +85,7 @@
     this.bc = bc;
   }
 
-  DatanodeDescriptor getDatanode(int index) {
+  public DatanodeDescriptor getDatanode(int index) {
     assert this.triplets != null : "BlockInfo is not initialized";
     assert index >= 0 && index*3 < triplets.length : "Index is out of bound";
     return (DatanodeDescriptor)triplets[index*3];
@@ -153,7 +153,7 @@
     return info;
   }
 
-  int getCapacity() {
+  public int getCapacity() {
     assert this.triplets != null : "BlockInfo is not initialized";
     assert triplets.length % 3 == 0 : "Malformed BlockInfo";
     return triplets.length / 3;
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java
index 4be0527..3504554 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockManager.java
@@ -3138,6 +3138,13 @@
         UnderReplicatedBlocks.QUEUE_WITH_CORRUPT_BLOCKS);
   }
 
+  /**
+   * Get the replicas which are corrupt for a given block.
+   */
+  public Collection<DatanodeDescriptor> getCorruptReplicas(Block block) {
+    return corruptReplicas.getNodes(block);
+  }
+
   /** @return the size of UnderReplicatedBlocks */
   public int numOfUnderReplicatedBlocks() {
     return neededReplications.size();
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/CacheReplicationMonitor.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/CacheReplicationMonitor.java
new file mode 100644
index 0000000..5d9c39c
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/CacheReplicationMonitor.java
@@ -0,0 +1,453 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.server.blockmanagement;
+
+import static org.apache.hadoop.util.ExitUtil.terminate;
+
+import java.io.Closeable;
+import java.io.IOException;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Random;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.fs.UnresolvedLinkException;
+import org.apache.hadoop.hdfs.protocol.Block;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheEntry;
+import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor.CachedBlocksList.Type;
+import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.BlockUCState;
+import org.apache.hadoop.hdfs.server.namenode.CacheManager;
+import org.apache.hadoop.hdfs.server.namenode.CachedBlock;
+import org.apache.hadoop.hdfs.server.namenode.FSDirectory;
+import org.apache.hadoop.hdfs.server.namenode.FSNamesystem;
+import org.apache.hadoop.hdfs.server.namenode.INode;
+import org.apache.hadoop.hdfs.server.namenode.INodeDirectory;
+import org.apache.hadoop.hdfs.server.namenode.INodeFile;
+import org.apache.hadoop.hdfs.util.ReadOnlyList;
+import org.apache.hadoop.util.GSet;
+import org.apache.hadoop.util.Time;
+
+/**
+ * Scans the namesystem, scheduling blocks to be cached as appropriate.
+ *
+ * The CacheReplicationMonitor does a full scan when the NameNode first
+ * starts up, and at configurable intervals afterwards.
+ */
+@InterfaceAudience.LimitedPrivate({"HDFS"})
+public class CacheReplicationMonitor extends Thread implements Closeable {
+
+  private static final Log LOG =
+      LogFactory.getLog(CacheReplicationMonitor.class);
+
+  private final FSNamesystem namesystem;
+
+  private final BlockManager blockManager;
+
+  private final CacheManager cacheManager;
+
+  private final GSet<CachedBlock, CachedBlock> cachedBlocks;
+
+  /**
+   * Pseudorandom number source
+   */
+  private final Random random = new Random();
+
+  /**
+   * The interval at which we scan the namesystem for caching changes.
+   */
+  private final long intervalMs;
+
+  /**
+   * True if we should rescan immediately, regardless of how much time
+   * elapsed since the previous scan.
+   */
+  private boolean rescanImmediately;
+
+  /**
+   * The monotonic time at which the current scan started.
+   */
+  private long scanTimeMs;
+
+  /**
+   * Mark status of the current scan.
+   */
+  private boolean mark = false;
+
+  /**
+   * True if this monitor should terminate.
+   */
+  private boolean shutdown;
+
+  /**
+   * Cache directives found in the previous scan.
+   */
+  private int scannedDirectives;
+
+  /**
+   * Blocks found in the previous scan.
+   */
+  private long scannedBlocks;
+  
+  public CacheReplicationMonitor(FSNamesystem namesystem,
+      CacheManager cacheManager, long intervalMs) {
+    this.namesystem = namesystem;
+    this.blockManager = namesystem.getBlockManager();
+    this.cacheManager = cacheManager;
+    this.cachedBlocks = cacheManager.getCachedBlocks();
+    this.intervalMs = intervalMs;
+  }
+
+  @Override
+  public void run() {
+    shutdown = false;
+    rescanImmediately = true;
+    scanTimeMs = 0;
+    LOG.info("Starting CacheReplicationMonitor with interval " +
+             intervalMs + " milliseconds");
+    try {
+      long curTimeMs = Time.monotonicNow();
+      while (true) {
+        synchronized(this) {
+          while (true) {
+            if (shutdown) {
+              LOG.info("Shutting down CacheReplicationMonitor");
+              return;
+            }
+            if (rescanImmediately) {
+              LOG.info("Rescanning on request");
+              rescanImmediately = false;
+              break;
+            }
+            long delta = (scanTimeMs + intervalMs) - curTimeMs;
+            if (delta <= 0) {
+              LOG.info("Rescanning after " + (curTimeMs - scanTimeMs) +
+                  " milliseconds");
+              break;
+            }
+            this.wait(delta);
+            curTimeMs = Time.monotonicNow();
+          }
+        }
+        scanTimeMs = curTimeMs;
+        mark = !mark;
+        rescan();
+        curTimeMs = Time.monotonicNow();
+        LOG.info("Scanned " + scannedDirectives + " directive(s) and " +
+            scannedBlocks + " block(s) in " + (curTimeMs - scanTimeMs) + " " +
+            "millisecond(s).");
+      }
+    } catch (Throwable t) {
+      LOG.fatal("Thread exiting", t);
+      terminate(1, t);
+    }
+  }
+
+  /**
+   * Kick the monitor thread.
+   * 
+   * If it is sleeping, it will wake up and start scanning.
+   * If it is currently scanning, it will finish the scan and immediately do 
+   * another one.
+   */
+  public synchronized void kick() {
+    rescanImmediately = true;
+    this.notifyAll();
+  }
+
+  /**
+   * Shut down and join the monitor thread.
+   */
+  @Override
+  public void close() throws IOException {
+    synchronized(this) {
+      if (shutdown) return;
+      shutdown = true;
+      this.notifyAll();
+    }
+    try {
+      if (this.isAlive()) {
+        this.join(60000);
+      }
+    } catch (InterruptedException e) {
+      Thread.currentThread().interrupt();
+    }
+  }
+
+  private void rescan() {
+    scannedDirectives = 0;
+    scannedBlocks = 0;
+    namesystem.writeLock();
+    try {
+      rescanPathBasedCacheEntries();
+    } finally {
+      namesystem.writeUnlock();
+    }
+    namesystem.writeLock();
+    try {
+      rescanCachedBlockMap();
+    } finally {
+      namesystem.writeUnlock();
+    }
+  }
+
+  /**
+   * Scan all PathBasedCacheEntries.  Use the information to figure out
+   * what cache replication factor each block should have.
+   *
+   * @param mark       Whether the current scan is setting or clearing the mark
+   */
+  private void rescanPathBasedCacheEntries() {
+    FSDirectory fsDir = namesystem.getFSDirectory();
+    for (PathBasedCacheEntry pce : cacheManager.getEntriesById().values()) {
+      scannedDirectives++;
+      String path = pce.getPath();
+      INode node;
+      try {
+        node = fsDir.getINode(path);
+      } catch (UnresolvedLinkException e) {
+        // We don't cache through symlinks
+        continue;
+      }
+      if (node == null)  {
+        if (LOG.isDebugEnabled()) {
+          LOG.debug("No inode found at " + path);
+        }
+      } else if (node.isDirectory()) {
+        INodeDirectory dir = node.asDirectory();
+        ReadOnlyList<INode> children = dir.getChildrenList(null);
+        for (INode child : children) {
+          if (child.isFile()) {
+            rescanFile(pce, child.asFile());
+          }
+        }
+      } else if (node.isFile()) {
+        rescanFile(pce, node.asFile());
+      } else {
+        if (LOG.isDebugEnabled()) {
+          LOG.debug("Ignoring non-directory, non-file inode " + node +
+                    " found at " + path);
+        }
+      }
+    }
+  }
+  
+  /**
+   * Apply a PathBasedCacheEntry to a file.
+   *
+   * @param pce       The PathBasedCacheEntry to apply.
+   * @param file      The file.
+   */
+  private void rescanFile(PathBasedCacheEntry pce, INodeFile file) {
+    BlockInfo[] blockInfos = file.getBlocks();
+    for (BlockInfo blockInfo : blockInfos) {
+      if (!blockInfo.getBlockUCState().equals(BlockUCState.COMPLETE)) {
+        // We don't try to cache blocks that are under construction.
+        continue;
+      }
+      Block block = new Block(blockInfo.getBlockId());
+      CachedBlock ncblock = new CachedBlock(block.getBlockId(),
+          pce.getReplication(), mark);
+      CachedBlock ocblock = cachedBlocks.get(ncblock);
+      if (ocblock == null) {
+        cachedBlocks.put(ncblock);
+      } else {
+        if (mark != ocblock.getMark()) {
+          // Mark hasn't been set in this scan, so update replication and mark.
+          ocblock.setReplicationAndMark(pce.getReplication(), mark);
+        } else {
+          // Mark already set in this scan.  Set replication to highest value in
+          // any PathBasedCacheEntry that covers this file.
+          ocblock.setReplicationAndMark((short)Math.max(
+              pce.getReplication(), ocblock.getReplication()), mark);
+        }
+      }
+    }
+  }
+
+  /**
+   * Scan through the cached block map.
+   * Any blocks which are under-replicated should be assigned new Datanodes.
+   * Blocks that are over-replicated should be removed from Datanodes.
+   */
+  private void rescanCachedBlockMap() {
+    for (Iterator<CachedBlock> cbIter = cachedBlocks.iterator();
+        cbIter.hasNext(); ) {
+      scannedBlocks++;
+      CachedBlock cblock = cbIter.next();
+      List<DatanodeDescriptor> pendingCached =
+          cblock.getDatanodes(Type.PENDING_CACHED);
+      List<DatanodeDescriptor> cached =
+          cblock.getDatanodes(Type.CACHED);
+      List<DatanodeDescriptor> pendingUncached =
+          cblock.getDatanodes(Type.PENDING_UNCACHED);
+      // Remove nodes from PENDING_UNCACHED if they were actually uncached.
+      for (Iterator<DatanodeDescriptor> iter = pendingUncached.iterator();
+          iter.hasNext(); ) {
+        DatanodeDescriptor datanode = iter.next();
+        if (!cblock.isInList(datanode.getCached())) {
+          datanode.getPendingUncached().remove(cblock);
+          iter.remove();
+        }
+      }
+      // If the block's mark doesn't match with the mark of this scan, that
+      // means that this block couldn't be reached during this scan.  That means
+      // it doesn't need to be cached any more.
+      int neededCached = (cblock.getMark() != mark) ?
+          0 : cblock.getReplication();
+      int numCached = cached.size();
+      if (numCached >= neededCached) {
+        // If we have enough replicas, drop all pending cached.
+        for (DatanodeDescriptor datanode : pendingCached) {
+          datanode.getPendingCached().remove(cblock);
+        }
+        pendingCached.clear();
+      }
+      if (numCached < neededCached) {
+        // If we don't have enough replicas, drop all pending uncached.
+        for (DatanodeDescriptor datanode : pendingUncached) {
+          datanode.getPendingUncached().remove(cblock);
+        }
+        pendingUncached.clear();
+      }
+      int neededUncached = numCached -
+          (pendingUncached.size() + neededCached);
+      if (neededUncached > 0) {
+        addNewPendingUncached(neededUncached, cblock, cached,
+            pendingUncached);
+      } else {
+        int additionalCachedNeeded = neededCached -
+            (numCached + pendingCached.size());
+        if (additionalCachedNeeded > 0) {
+          addNewPendingCached(additionalCachedNeeded, cblock, cached,
+              pendingCached);
+        }
+      }
+      if ((neededCached == 0) &&
+          pendingUncached.isEmpty() &&
+          pendingCached.isEmpty()) {
+        // we have nothing more to do with this block.
+        cbIter.remove();
+      }
+    }
+  }
+
+  /**
+   * Add new entries to the PendingUncached list.
+   *
+   * @param neededUncached   The number of replicas that need to be uncached.
+   * @param cachedBlock      The block which needs to be uncached.
+   * @param cached           A list of DataNodes currently caching the block.
+   * @param pendingUncached  A list of DataNodes that will soon uncache the
+   *                         block.
+   */
+  private void addNewPendingUncached(int neededUncached,
+      CachedBlock cachedBlock, List<DatanodeDescriptor> cached,
+      List<DatanodeDescriptor> pendingUncached) {
+    if (!cacheManager.isActive()) {
+      return;
+    }
+    // Figure out which replicas can be uncached.
+    LinkedList<DatanodeDescriptor> possibilities =
+        new LinkedList<DatanodeDescriptor>();
+    for (DatanodeDescriptor datanode : cached) {
+      if (!pendingUncached.contains(datanode)) {
+        possibilities.add(datanode);
+      }
+    }
+    while (neededUncached > 0) {
+      if (possibilities.isEmpty()) {
+        LOG.warn("Logic error: we're trying to uncache more replicas than " +
+            "actually exist for " + cachedBlock);
+        return;
+      }
+      DatanodeDescriptor datanode =
+        possibilities.remove(random.nextInt(possibilities.size()));
+      pendingUncached.add(datanode);
+      boolean added = datanode.getPendingUncached().add(cachedBlock);
+      assert added;
+      neededUncached--;
+    }
+  }
+  
+  /**
+   * Add new entries to the PendingCached list.
+   *
+   * @param neededCached     The number of replicas that need to be cached.
+   * @param cachedBlock      The block which needs to be cached.
+   * @param cached           A list of DataNodes currently caching the block.
+   * @param pendingCached    A list of DataNodes that will soon cache the
+   *                         block.
+   */
+  private void addNewPendingCached(int neededCached,
+      CachedBlock cachedBlock, List<DatanodeDescriptor> cached,
+      List<DatanodeDescriptor> pendingCached) {
+    if (!cacheManager.isActive()) {
+      return;
+    }
+    // To figure out which replicas can be cached, we consult the
+    // blocksMap.  We don't want to try to cache a corrupt replica, though.
+    BlockInfo blockInfo = blockManager.
+          getStoredBlock(new Block(cachedBlock.getBlockId()));
+    if (blockInfo == null) {
+      LOG.debug("Not caching block " + cachedBlock + " because it " +
+          "was deleted from all DataNodes.");
+      return;
+    }
+    if (!blockInfo.isComplete()) {
+      if (LOG.isDebugEnabled()) {
+        LOG.debug("Not caching block " + cachedBlock + " because it " +
+            "is not yet complete.");
+      }
+      return;
+    }
+    List<DatanodeDescriptor> possibilities = new LinkedList<DatanodeDescriptor>();
+    int numReplicas = blockInfo.getCapacity();
+    Collection<DatanodeDescriptor> corrupt =
+        blockManager.getCorruptReplicas(blockInfo);
+    for (int i = 0; i < numReplicas; i++) {
+      DatanodeDescriptor datanode = blockInfo.getDatanode(i);
+      if ((datanode != null) && 
+          ((!pendingCached.contains(datanode)) &&
+          ((corrupt == null) || (!corrupt.contains(datanode))))) {
+        possibilities.add(datanode);
+      }
+    }
+    while (neededCached > 0) {
+      if (possibilities.isEmpty()) {
+        LOG.warn("We need " + neededCached + " more replica(s) than " +
+            "actually exist to provide a cache replication of " +
+            cachedBlock.getReplication() + " for " + cachedBlock);
+        return;
+      }
+      DatanodeDescriptor datanode =
+          possibilities.remove(random.nextInt(possibilities.size()));
+      if (LOG.isDebugEnabled()) {
+        LOG.debug("AddNewPendingCached: datanode " + datanode + 
+            " will now cache block " + cachedBlock);
+      }
+      pendingCached.add(datanode);
+      boolean added = datanode.getPendingCached().add(cachedBlock);
+      assert added;
+      neededCached--;
+    }
+  }
+}
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DatanodeDescriptor.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DatanodeDescriptor.java
index b2ab1a7..f7b43e4 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DatanodeDescriptor.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DatanodeDescriptor.java
@@ -22,14 +22,20 @@
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Queue;
+
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
 import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.protocol.DatanodeID;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
+import org.apache.hadoop.hdfs.server.namenode.CachedBlock;
 import org.apache.hadoop.hdfs.util.LightWeightHashSet;
+import org.apache.hadoop.util.IntrusiveCollection;
 import org.apache.hadoop.util.Time;
 
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Preconditions;
+
 /**
  * This class extends the DatanodeInfo class with ephemeral information (eg
  * health, capacity, what blocks are associated with the Datanode) that is
@@ -94,8 +100,74 @@
     }
   }
 
+  /**
+   * A list of CachedBlock objects on this datanode.
+   */
+  public static class CachedBlocksList extends IntrusiveCollection<CachedBlock> {
+    public enum Type {
+      PENDING_CACHED,
+      CACHED,
+      PENDING_UNCACHED
+    }
+
+    private final DatanodeDescriptor datanode;
+
+    private final Type type;
+
+    CachedBlocksList(DatanodeDescriptor datanode, Type type) {
+      this.datanode = datanode;
+      this.type = type;
+    }
+
+    public DatanodeDescriptor getDatanode() {
+      return datanode;
+    }
+
+    public Type getType() {
+      return type;
+    }
+  }
+
+  /**
+   * The blocks which we want to cache on this DataNode.
+   */
+  private final CachedBlocksList pendingCached = 
+      new CachedBlocksList(this, CachedBlocksList.Type.PENDING_CACHED);
+
+  /**
+   * The blocks which we know are cached on this datanode.
+   * This list is updated by periodic cache reports.
+   */
+  private final CachedBlocksList cached = 
+      new CachedBlocksList(this, CachedBlocksList.Type.CACHED);
+
+  /**
+   * The blocks which we want to uncache on this DataNode.
+   */
+  private final CachedBlocksList pendingUncached = 
+      new CachedBlocksList(this, CachedBlocksList.Type.PENDING_UNCACHED);
+
+  public CachedBlocksList getPendingCached() {
+    return pendingCached;
+  }
+
+  public CachedBlocksList getCached() {
+    return cached;
+  }
+
+  public CachedBlocksList getPendingUncached() {
+    return pendingUncached;
+  }
+
+  /**
+   * Head of the list of blocks on the datanode
+   */
   private volatile BlockInfo blockList = null;
+  /**
+   * Number of blocks on the datanode
+   */
   private int numBlocks = 0;
+
   // isAlive == heartbeats.contains(this)
   // This is an optimization, because contains takes O(n) time on Arraylist
   public boolean isAlive = false;
@@ -160,7 +232,7 @@
    * @param nodeID id of the data node
    */
   public DatanodeDescriptor(DatanodeID nodeID) {
-    this(nodeID, 0L, 0L, 0L, 0L, 0, 0);
+    this(nodeID, 0L, 0L, 0L, 0L, 0L, 0L, 0, 0);
   }
 
   /**
@@ -170,7 +242,7 @@
    */
   public DatanodeDescriptor(DatanodeID nodeID, 
                             String networkLocation) {
-    this(nodeID, networkLocation, 0L, 0L, 0L, 0L, 0, 0);
+    this(nodeID, networkLocation, 0L, 0L, 0L, 0L, 0L, 0L, 0, 0);
   }
   
   /**
@@ -180,6 +252,8 @@
    * @param dfsUsed space used by the data node
    * @param remaining remaining capacity of the data node
    * @param bpused space used by the block pool corresponding to this namenode
+   * @param cacheCapacity cache capacity of the data node
+   * @param cacheUsed cache used on the data node
    * @param xceiverCount # of data transfers at the data node
    */
   public DatanodeDescriptor(DatanodeID nodeID, 
@@ -187,11 +261,13 @@
                             long dfsUsed,
                             long remaining,
                             long bpused,
+                            long cacheCapacity,
+                            long cacheUsed,
                             int xceiverCount,
                             int failedVolumes) {
     super(nodeID);
-    updateHeartbeat(capacity, dfsUsed, remaining, bpused, xceiverCount, 
-        failedVolumes);
+    updateHeartbeat(capacity, dfsUsed, remaining, bpused, cacheCapacity,
+        cacheUsed, xceiverCount, failedVolumes);
   }
 
   /**
@@ -202,6 +278,8 @@
    * @param dfsUsed the used space by dfs datanode
    * @param remaining remaining capacity of the data node
    * @param bpused space used by the block pool corresponding to this namenode
+   * @param cacheCapacity cache capacity of the data node
+   * @param cacheUsed cache used on the data node
    * @param xceiverCount # of data transfers at the data node
    */
   public DatanodeDescriptor(DatanodeID nodeID,
@@ -210,11 +288,13 @@
                             long dfsUsed,
                             long remaining,
                             long bpused,
+                            long cacheCapacity,
+                            long cacheUsed,
                             int xceiverCount,
                             int failedVolumes) {
     super(nodeID, networkLocation);
-    updateHeartbeat(capacity, dfsUsed, remaining, bpused, xceiverCount, 
-        failedVolumes);
+    updateHeartbeat(capacity, dfsUsed, remaining, bpused, cacheCapacity,
+        cacheUsed, xceiverCount, failedVolumes);
   }
 
   /**
@@ -257,6 +337,7 @@
    * Used for testing only
    * @return the head of the blockList
    */
+  @VisibleForTesting
   protected BlockInfo getHead(){
     return blockList;
   }
@@ -285,6 +366,11 @@
     this.blockList = null;
     this.invalidateBlocks.clear();
     this.volumeFailures = 0;
+    // pendingCached, cached, and pendingUncached are protected by the
+    // FSN lock.
+    this.pendingCached.clear();
+    this.cached.clear();
+    this.pendingUncached.clear();
   }
   
   public void clearBlockQueues() {
@@ -293,6 +379,11 @@
       this.recoverBlocks.clear();
       this.replicateBlocks.clear();
     }
+    // pendingCached, cached, and pendingUncached are protected by the
+    // FSN lock.
+    this.pendingCached.clear();
+    this.cached.clear();
+    this.pendingUncached.clear();
   }
 
   public int numBlocks() {
@@ -303,11 +394,14 @@
    * Updates stats from datanode heartbeat.
    */
   public void updateHeartbeat(long capacity, long dfsUsed, long remaining,
-      long blockPoolUsed, int xceiverCount, int volFailures) {
+      long blockPoolUsed, long cacheCapacity, long cacheUsed, int xceiverCount,
+      int volFailures) {
     setCapacity(capacity);
     setRemaining(remaining);
     setBlockPoolUsed(blockPoolUsed);
     setDfsUsed(dfsUsed);
+    setCacheCapacity(cacheCapacity);
+    setCacheUsed(cacheUsed);
     setXceiverCount(xceiverCount);
     setLastUpdate(Time.now());    
     this.volumeFailures = volFailures;
@@ -348,7 +442,7 @@
   public Iterator<BlockInfo> getBlockIterator() {
     return new BlockIterator(this.blockList, this);
   }
-  
+
   /**
    * Store block replication work.
    */
@@ -380,7 +474,7 @@
       }
     }
   }
-
+  
   /**
    * The number of work items that are pending to be replicated
    */
@@ -397,7 +491,7 @@
       return invalidateBlocks.size();
     }
   }
-  
+
   public List<BlockTargetPair> getReplicationCommand(int maxTransfers) {
     return replicateBlocks.poll(maxTransfers);
   }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DatanodeManager.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DatanodeManager.java
index cc50122..2ecfde8 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DatanodeManager.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DatanodeManager.java
@@ -32,6 +32,8 @@
 import org.apache.hadoop.hdfs.protocol.*;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants.DatanodeReportType;
 import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor.BlockTargetPair;
+import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor.CachedBlocksList;
+import org.apache.hadoop.hdfs.server.namenode.CachedBlock;
 import org.apache.hadoop.hdfs.server.namenode.HostFileManager;
 import org.apache.hadoop.hdfs.server.namenode.HostFileManager.Entry;
 import org.apache.hadoop.hdfs.server.namenode.HostFileManager.EntrySet;
@@ -45,6 +47,7 @@
 import org.apache.hadoop.net.*;
 import org.apache.hadoop.net.NetworkTopology.InvalidTopologyException;
 import org.apache.hadoop.util.Daemon;
+import org.apache.hadoop.util.IntrusiveCollection;
 import org.apache.hadoop.util.ReflectionUtils;
 import org.apache.hadoop.util.Time;
 
@@ -144,6 +147,12 @@
 
   private final boolean checkIpHostnameInRegistration;
   /**
+   * Whether we should tell datanodes what to cache in replies to
+   * heartbeat messages.
+   */
+  private boolean sendCachingCommands = false;
+
+  /**
    * The number of datanodes for each software version. This list should change
    * during rolling upgrades.
    * Software version -> Number of datanodes with this version
@@ -1215,8 +1224,8 @@
   public DatanodeCommand[] handleHeartbeat(DatanodeRegistration nodeReg,
       final String blockPoolId,
       long capacity, long dfsUsed, long remaining, long blockPoolUsed,
-      int xceiverCount, int maxTransfers, int failedVolumes
-      ) throws IOException {
+      long cacheCapacity, long cacheUsed, int xceiverCount, int maxTransfers,
+      int failedVolumes) throws IOException {
     synchronized (heartbeatManager) {
       synchronized (datanodeMap) {
         DatanodeDescriptor nodeinfo = null;
@@ -1237,7 +1246,8 @@
         }
 
         heartbeatManager.updateHeartbeat(nodeinfo, capacity, dfsUsed,
-            remaining, blockPoolUsed, xceiverCount, failedVolumes);
+            remaining, blockPoolUsed, cacheCapacity, cacheUsed, xceiverCount,
+            failedVolumes);
 
         // If we are in safemode, do not send back any recovery / replication
         // requests. Don't even drain the existing queue of work.
@@ -1298,7 +1308,19 @@
           cmds.add(new BlockCommand(DatanodeProtocol.DNA_INVALIDATE,
               blockPoolId, blks));
         }
-        
+        DatanodeCommand pendingCacheCommand =
+            getCacheCommand(nodeinfo.getPendingCached(), nodeinfo,
+              DatanodeProtocol.DNA_CACHE, blockPoolId);
+        if (pendingCacheCommand != null) {
+          cmds.add(pendingCacheCommand);
+        }
+        DatanodeCommand pendingUncacheCommand =
+            getCacheCommand(nodeinfo.getPendingUncached(), nodeinfo,
+              DatanodeProtocol.DNA_UNCACHE, blockPoolId);
+        if (pendingUncacheCommand != null) {
+          cmds.add(pendingUncacheCommand);
+        }
+
         blockManager.addKeyUpdateCommand(cmds, nodeinfo);
 
         // check for balancer bandwidth update
@@ -1318,6 +1340,40 @@
   }
 
   /**
+   * Convert a CachedBlockList into a DatanodeCommand with a list of blocks.
+   *
+   * @param list       The {@link CachedBlocksList}.  This function 
+   *                   clears the list.
+   * @param datanode   The datanode.
+   * @param action     The action to perform in the command.
+   * @param poolId     The block pool id.
+   * @return           A DatanodeCommand to be sent back to the DN, or null if
+   *                   there is nothing to be done.
+   */
+  private DatanodeCommand getCacheCommand(CachedBlocksList list,
+      DatanodeDescriptor datanode, int action, String poolId) {
+    int length = list.size();
+    if (length == 0) {
+      return null;
+    }
+    // Read and clear the existing cache commands.
+    long[] blockIds = new long[length];
+    int i = 0;
+    for (Iterator<CachedBlock> iter = list.iterator();
+            iter.hasNext(); ) {
+      CachedBlock cachedBlock = iter.next();
+      blockIds[i++] = cachedBlock.getBlockId();
+      iter.remove();
+    }
+    if (!sendCachingCommands) {
+      // Do not send caching commands unless the FSNamesystem told us we
+      // should.
+      return null;
+    }
+    return new BlockIdCommand(action, poolId, blockIds);
+  }
+
+  /**
    * Tell all datanodes to use a new, non-persistent bandwidth value for
    * dfs.balance.bandwidthPerSec.
    *
@@ -1365,4 +1421,8 @@
   public String toString() {
     return getClass().getSimpleName() + ": " + host2DatanodeMap;
   }
+
+  public void setSendCachingCommands(boolean sendCachingCommands) {
+    this.sendCachingCommands = sendCachingCommands;
+  }
 }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/HeartbeatManager.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/HeartbeatManager.java
index 0bff1bf..f9c28e9 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/HeartbeatManager.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/HeartbeatManager.java
@@ -170,7 +170,7 @@
       addDatanode(d);
 
       //update its timestamp
-      d.updateHeartbeat(0L, 0L, 0L, 0L, 0, 0);
+      d.updateHeartbeat(0L, 0L, 0L, 0L, 0L, 0L, 0, 0);
     }
   }
 
@@ -193,10 +193,10 @@
 
   synchronized void updateHeartbeat(final DatanodeDescriptor node,
       long capacity, long dfsUsed, long remaining, long blockPoolUsed,
-      int xceiverCount, int failedVolumes) {
+      long cacheCapacity, long cacheUsed, int xceiverCount, int failedVolumes) {
     stats.subtract(node);
     node.updateHeartbeat(capacity, dfsUsed, remaining, blockPoolUsed,
-        xceiverCount, failedVolumes);
+        cacheCapacity, cacheUsed, xceiverCount, failedVolumes);
     stats.add(node);
   }
 
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPOfferService.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPOfferService.java
index d5e026b..7fca64b 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPOfferService.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPOfferService.java
@@ -33,6 +33,7 @@
 import org.apache.hadoop.hdfs.protocolPB.DatanodeProtocolClientSideTranslatorPB;
 import org.apache.hadoop.hdfs.server.protocol.BalancerBandwidthCommand;
 import org.apache.hadoop.hdfs.server.protocol.BlockCommand;
+import org.apache.hadoop.hdfs.server.protocol.BlockIdCommand;
 import org.apache.hadoop.hdfs.server.protocol.BlockRecoveryCommand;
 import org.apache.hadoop.hdfs.server.protocol.DatanodeCommand;
 import org.apache.hadoop.hdfs.server.protocol.DatanodeProtocol;
@@ -518,6 +519,8 @@
       return true;
     final BlockCommand bcmd = 
       cmd instanceof BlockCommand? (BlockCommand)cmd: null;
+    final BlockIdCommand blockIdCmd = 
+      cmd instanceof BlockIdCommand ? (BlockIdCommand)cmd: null;
 
     switch(cmd.getAction()) {
     case DatanodeProtocol.DNA_TRANSFER:
@@ -543,6 +546,16 @@
       }
       dn.metrics.incrBlocksRemoved(toDelete.length);
       break;
+    case DatanodeProtocol.DNA_CACHE:
+      LOG.info("DatanodeCommand action: DNA_CACHE");
+      dn.getFSDataset().cache(blockIdCmd.getBlockPoolId(), blockIdCmd.getBlockIds());
+      dn.metrics.incrBlocksCached(blockIdCmd.getBlockIds().length);
+      break;
+    case DatanodeProtocol.DNA_UNCACHE:
+      LOG.info("DatanodeCommand action: DNA_UNCACHE");
+      dn.getFSDataset().uncache(blockIdCmd.getBlockPoolId(), blockIdCmd.getBlockIds());
+      dn.metrics.incrBlocksUncached(blockIdCmd.getBlockIds().length);
+      break;
     case DatanodeProtocol.DNA_SHUTDOWN:
       // TODO: DNA_SHUTDOWN appears to be unused - the NN never sends this command
       // See HDFS-2987.
@@ -615,6 +628,8 @@
     case DatanodeProtocol.DNA_FINALIZE:
     case DatanodeProtocol.DNA_RECOVERBLOCK:
     case DatanodeProtocol.DNA_BALANCERBANDWIDTHUPDATE:
+    case DatanodeProtocol.DNA_CACHE:
+    case DatanodeProtocol.DNA_UNCACHE:
       LOG.warn("Got a command from standby NN - ignoring command:" + cmd.getAction());
       break;
     default:
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java
index 75f42f9..73d3cdf 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java
@@ -24,6 +24,7 @@
 import java.net.SocketTimeoutException;
 import java.net.URI;
 import java.util.Collection;
+import java.util.List;
 import java.util.Map;
 
 import org.apache.commons.logging.Log;
@@ -84,6 +85,8 @@
 
   boolean resetBlockReportTime = true;
 
+  volatile long lastCacheReport = 0;
+
   Thread bpThread;
   DatanodeProtocolClientSideTranslatorPB bpNamenode;
   private volatile long lastHeartbeat = 0;
@@ -430,6 +433,35 @@
     return cmd;
   }
   
+  DatanodeCommand cacheReport() throws IOException {
+    // If caching is disabled, do not send a cache report
+    if (dn.getFSDataset().getDnCacheCapacity() == 0) {
+      return null;
+    }
+    // send cache report if timer has expired.
+    DatanodeCommand cmd = null;
+    long startTime = Time.monotonicNow();
+    if (startTime - lastCacheReport > dnConf.cacheReportInterval) {
+      if (LOG.isDebugEnabled()) {
+        LOG.debug("Sending cacheReport from service actor: " + this);
+      }
+      lastCacheReport = startTime;
+
+      String bpid = bpos.getBlockPoolId();
+      List<Long> blockIds = dn.getFSDataset().getCacheReport(bpid);
+      long createTime = Time.monotonicNow();
+
+      cmd = bpNamenode.cacheReport(bpRegistration, bpid, blockIds);
+      long sendTime = Time.monotonicNow();
+      long createCost = createTime - startTime;
+      long sendCost = sendTime - createTime;
+      dn.getMetrics().addCacheReport(sendCost);
+      LOG.info("CacheReport of " + blockIds.size()
+          + " blocks took " + createCost + " msec to generate and "
+          + sendCost + " msecs for RPC and NN processing");
+    }
+    return cmd;
+  }
   
   HeartbeatResponse sendHeartBeat() throws IOException {
     if (LOG.isDebugEnabled()) {
@@ -443,6 +475,8 @@
         dn.getFSDataset().getRemaining(),
         dn.getFSDataset().getBlockPoolUsed(bpos.getBlockPoolId())) };
     return bpNamenode.sendHeartbeat(bpRegistration, report,
+        dn.getFSDataset().getDnCacheCapacity(),
+        dn.getFSDataset().getDnCacheUsed(),
         dn.getXmitsInProgress(),
         dn.getXceiverCount(),
         dn.getFSDataset().getNumFailedVolumes());
@@ -496,11 +530,12 @@
    * forever calling remote NameNode functions.
    */
   private void offerService() throws Exception {
-    LOG.info("For namenode " + nnAddr + " using DELETEREPORT_INTERVAL of "
-        + dnConf.deleteReportInterval + " msec " + " BLOCKREPORT_INTERVAL of "
-        + dnConf.blockReportInterval + "msec" + " Initial delay: "
-        + dnConf.initialBlockReportDelay + "msec" + "; heartBeatInterval="
-        + dnConf.heartBeatInterval);
+    LOG.info("For namenode " + nnAddr + " using"
+        + " DELETEREPORT_INTERVAL of " + dnConf.deleteReportInterval + " msec "
+        + " BLOCKREPORT_INTERVAL of " + dnConf.blockReportInterval + "msec"
+        + " CACHEREPORT_INTERVAL of " + dnConf.cacheReportInterval + "msec"
+        + " Initial delay: " + dnConf.initialBlockReportDelay + "msec"
+        + "; heartBeatInterval=" + dnConf.heartBeatInterval);
 
     //
     // Now loop for a long time....
@@ -555,6 +590,9 @@
         DatanodeCommand cmd = blockReport();
         processCommand(new DatanodeCommand[]{ cmd });
 
+        cmd = cacheReport();
+        processCommand(new DatanodeCommand[]{ cmd });
+
         // Now safe to start scanning the block pool.
         // If it has already been started, this is a no-op.
         if (dn.blockScanner != null) {
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DNConf.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DNConf.java
index 1577d78..5d7afc7 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DNConf.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DNConf.java
@@ -18,13 +18,18 @@
 package org.apache.hadoop.hdfs.server.datanode;
 
 import org.apache.hadoop.classification.InterfaceAudience;
+
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_BLOCKREPORT_INITIAL_DELAY_DEFAULT;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_BLOCKREPORT_INITIAL_DELAY_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_BLOCKREPORT_INTERVAL_MSEC_DEFAULT;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_BLOCKREPORT_INTERVAL_MSEC_KEY;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_CACHEREPORT_INTERVAL_MSEC_DEFAULT;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_CACHEREPORT_INTERVAL_MSEC_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_CLIENT_SOCKET_TIMEOUT_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_CLIENT_WRITE_PACKET_SIZE_DEFAULT;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_CLIENT_WRITE_PACKET_SIZE_KEY;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_MAX_LOCKED_MEMORY_DEFAULT;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_MAX_LOCKED_MEMORY_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_SOCKET_WRITE_TIMEOUT_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_SYNCONCLOSE_DEFAULT;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_SYNCONCLOSE_KEY;
@@ -39,6 +44,7 @@
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_ENCRYPT_DATA_TRANSFER_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_ENCRYPT_DATA_TRANSFER_DEFAULT;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATA_ENCRYPTION_ALGORITHM_KEY;
+
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants;
@@ -66,6 +72,7 @@
   final long blockReportInterval;
   final long deleteReportInterval;
   final long initialBlockReportDelay;
+  final long cacheReportInterval;
   final int writePacketSize;
   
   final String minimumNameNodeVersion;
@@ -73,6 +80,8 @@
   
   final long xceiverStopTimeout;
 
+  final long maxLockedMemory;
+
   public DNConf(Configuration conf) {
     socketTimeout = conf.getInt(DFS_CLIENT_SOCKET_TIMEOUT_KEY,
         HdfsServerConstants.READ_TIMEOUT);
@@ -107,7 +116,9 @@
         DFSConfigKeys.DFS_DATANODE_USE_DN_HOSTNAME,
         DFSConfigKeys.DFS_DATANODE_USE_DN_HOSTNAME_DEFAULT);
     this.blockReportInterval = conf.getLong(DFS_BLOCKREPORT_INTERVAL_MSEC_KEY,
-    DFS_BLOCKREPORT_INTERVAL_MSEC_DEFAULT);
+        DFS_BLOCKREPORT_INTERVAL_MSEC_DEFAULT);
+    this.cacheReportInterval = conf.getLong(DFS_CACHEREPORT_INTERVAL_MSEC_KEY,
+        DFS_CACHEREPORT_INTERVAL_MSEC_DEFAULT);
     
     long initBRDelay = conf.getLong(
         DFS_BLOCKREPORT_INITIAL_DELAY_KEY,
@@ -137,6 +148,10 @@
     this.xceiverStopTimeout = conf.getLong(
         DFS_DATANODE_XCEIVER_STOP_TIMEOUT_MILLIS_KEY,
         DFS_DATANODE_XCEIVER_STOP_TIMEOUT_MILLIS_DEFAULT);
+
+    this.maxLockedMemory = conf.getLong(
+        DFS_DATANODE_MAX_LOCKED_MEMORY_KEY,
+        DFS_DATANODE_MAX_LOCKED_MEMORY_DEFAULT);
   }
   
   // We get minimumNameNodeVersion via a method so it can be mocked out in tests.
@@ -147,4 +162,8 @@
   public long getXceiverStopTimeout() {
     return xceiverStopTimeout;
   }
+
+  public long getMaxLockedMemory() {
+    return maxLockedMemory;
+  }
 }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java
index 2cc8e62..fee8419 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java
@@ -67,6 +67,7 @@
 import org.apache.hadoop.http.HttpServer;
 import org.apache.hadoop.io.IOUtils;
 import org.apache.hadoop.io.ReadaheadPool;
+import org.apache.hadoop.io.nativeio.NativeIO;
 import org.apache.hadoop.ipc.ProtobufRpcEngine;
 import org.apache.hadoop.ipc.RPC;
 import org.apache.hadoop.ipc.RemoteException;
@@ -656,6 +657,25 @@
     this.conf = conf;
     this.dnConf = new DNConf(conf);
 
+    if (dnConf.maxLockedMemory > 0) {
+      if (!NativeIO.isAvailable()) {
+        throw new RuntimeException(String.format(
+            "Cannot start datanode because the configured max locked memory" +
+            " size (%s) is greater than zero and native code is not available.",
+            DFS_DATANODE_MAX_LOCKED_MEMORY_KEY));
+      }
+      long ulimit = NativeIO.getMemlockLimit();
+      if (dnConf.maxLockedMemory > ulimit) {
+      throw new RuntimeException(String.format(
+          "Cannot start datanode because the configured max locked memory" +
+          " size (%s) of %d bytes is more than the datanode's available" +
+          " RLIMIT_MEMLOCK ulimit of %d bytes.",
+          DFS_DATANODE_MAX_LOCKED_MEMORY_KEY,
+          dnConf.maxLockedMemory,
+          ulimit));
+      }
+    }
+
     storage = new DataStorage();
     
     // global DN settings
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/FsDatasetSpi.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/FsDatasetSpi.java
index 4f63397..4c7edd7 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/FsDatasetSpi.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/FsDatasetSpi.java
@@ -269,6 +269,14 @@
    */
   public BlockListAsLongs getBlockReport(String bpid);
 
+  /**
+   * Returns the cache report - the full list of cached block IDs of a
+   * block pool.
+   * @param   bpid Block Pool Id
+   * @return  the cache report - the full list of cached block IDs.
+   */
+  public List<Long> getCacheReport(String bpid);
+
   /** Does the dataset contain the block? */
   public boolean contains(ExtendedBlock block);
 
@@ -294,6 +302,20 @@
    */
   public void invalidate(String bpid, Block invalidBlks[]) throws IOException;
 
+  /**
+   * Caches the specified blocks
+   * @param bpid Block pool id
+   * @param blockIds - block ids to cache
+   */
+  public void cache(String bpid, long[] blockIds);
+
+  /**
+   * Uncaches the specified blocks
+   * @param bpid Block pool id
+   * @param blockIds - blocks ids to uncache
+   */
+  public void uncache(String bpid, long[] blockIds);
+
     /**
      * Check if all the data directories are healthy
      * @throws DiskErrorException
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetCache.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetCache.java
new file mode 100644
index 0000000..6a68e63
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetCache.java
@@ -0,0 +1,223 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.hdfs.server.datanode.fsdataset.impl;
+
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.atomic.AtomicLong;
+
+import org.apache.commons.io.IOUtils;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+import org.apache.hadoop.fs.ChecksumException;
+import org.apache.hadoop.hdfs.DFSConfigKeys;
+import org.apache.hadoop.hdfs.protocol.Block;
+import org.apache.hadoop.hdfs.protocol.BlockListAsLongs;
+
+/**
+ * Manages caching for an FsDatasetImpl by using the mmap(2) and mlock(2)
+ * system calls to lock blocks into memory. Block checksums are verified upon
+ * entry into the cache.
+ */
+@InterfaceAudience.Private
+@InterfaceStability.Unstable
+public class FsDatasetCache {
+
+  private static final Log LOG = LogFactory.getLog(FsDatasetCache.class);
+
+  /**
+   * Map of cached blocks
+   */
+  private final ConcurrentMap<Long, MappableBlock> cachedBlocks;
+
+  private final FsDatasetImpl dataset;
+  /**
+   * Number of cached bytes
+   */
+  private AtomicLong usedBytes;
+  /**
+   * Total cache capacity in bytes
+   */
+  private final long maxBytes;
+
+  public FsDatasetCache(FsDatasetImpl dataset) {
+    this.dataset = dataset;
+    this.cachedBlocks = new ConcurrentHashMap<Long, MappableBlock>();
+    this.usedBytes = new AtomicLong(0);
+    this.maxBytes = dataset.datanode.getDnConf().getMaxLockedMemory();
+  }
+
+  /**
+   * @return if the block is cached
+   */
+  boolean isCached(String bpid, long blockId) {
+    MappableBlock mapBlock = cachedBlocks.get(blockId);
+    if (mapBlock != null) {
+      return mapBlock.getBlockPoolId().equals(bpid);
+    }
+    return false;
+  }
+
+  /**
+   * @return List of cached blocks suitable for translation into a
+   * {@link BlockListAsLongs} for a cache report.
+   */
+  List<Long> getCachedBlocks(String bpid) {
+    List<Long> blocks = new ArrayList<Long>();
+    // ConcurrentHashMap iteration doesn't see latest updates, which is okay
+    Iterator<MappableBlock> it = cachedBlocks.values().iterator();
+    while (it.hasNext()) {
+      MappableBlock mapBlock = it.next();
+      if (mapBlock.getBlockPoolId().equals(bpid)) {
+        blocks.add(mapBlock.getBlock().getBlockId());
+      }
+    }
+    return blocks;
+  }
+
+  /**
+   * Asynchronously attempts to cache a block. This is subject to the
+   * configured maximum locked memory limit.
+   * 
+   * @param block block to cache
+   * @param volume volume of the block
+   * @param blockIn stream of the block's data file
+   * @param metaIn stream of the block's meta file
+   */
+  void cacheBlock(String bpid, Block block, FsVolumeImpl volume,
+      FileInputStream blockIn, FileInputStream metaIn) {
+    if (isCached(bpid, block.getBlockId())) {
+      return;
+    }
+    MappableBlock mapBlock = null;
+    try {
+      mapBlock = new MappableBlock(bpid, block, volume, blockIn, metaIn);
+    } catch (IOException e) {
+      LOG.warn("Failed to cache replica " + block + ": Could not instantiate"
+          + " MappableBlock", e);
+      IOUtils.closeQuietly(blockIn);
+      IOUtils.closeQuietly(metaIn);
+      return;
+    }
+    // Check if there's sufficient cache capacity
+    boolean success = false;
+    long bytes = mapBlock.getNumBytes();
+    long used = usedBytes.get();
+    while (used+bytes < maxBytes) {
+      if (usedBytes.compareAndSet(used, used+bytes)) {
+        success = true;
+        break;
+      }
+      used = usedBytes.get();
+    }
+    if (!success) {
+      LOG.warn(String.format(
+          "Failed to cache replica %s: %s exceeded (%d + %d > %d)",
+          mapBlock.getBlock().toString(),
+          DFSConfigKeys.DFS_DATANODE_MAX_LOCKED_MEMORY_KEY,
+          used, bytes, maxBytes));
+      mapBlock.close();
+      return;
+    }
+    // Submit it to the worker pool to be cached
+    volume.getExecutor().execute(new WorkerTask(mapBlock));
+  }
+
+  /**
+   * Uncaches a block if it is cached.
+   * @param blockId id to uncache
+   */
+  void uncacheBlock(String bpid, long blockId) {
+    MappableBlock mapBlock = cachedBlocks.get(blockId);
+    if (mapBlock != null &&
+        mapBlock.getBlockPoolId().equals(bpid) &&
+        mapBlock.getBlock().getBlockId() == blockId) {
+      mapBlock.close();
+      cachedBlocks.remove(blockId);
+      long bytes = mapBlock.getNumBytes();
+      long used = usedBytes.get();
+      while (!usedBytes.compareAndSet(used, used - bytes)) {
+        used = usedBytes.get();
+      }
+      LOG.info("Successfully uncached block " + blockId);
+    } else {
+      LOG.info("Could not uncache block " + blockId + ": unknown block.");
+    }
+  }
+
+  /**
+   * Background worker that mmaps, mlocks, and checksums a block
+   */
+  private class WorkerTask implements Runnable {
+
+    private MappableBlock block;
+    WorkerTask(MappableBlock block) {
+      this.block = block;
+    }
+
+    @Override
+    public void run() {
+      boolean success = false;
+      try {
+        block.map();
+        block.lock();
+        block.verifyChecksum();
+        success = true;
+      } catch (ChecksumException e) {
+        // Exception message is bogus since this wasn't caused by a file read
+        LOG.warn("Failed to cache block " + block.getBlock() + ": Checksum "
+            + "verification failed.");
+      } catch (IOException e) {
+        LOG.warn("Failed to cache block " + block.getBlock() + ": IOException",
+            e);
+      }
+      // If we failed or the block became uncacheable in the meantime,
+      // clean up and return the reserved cache allocation 
+      if (!success || 
+          !dataset.validToCache(block.getBlockPoolId(),
+              block.getBlock().getBlockId())) {
+        block.close();
+        long used = usedBytes.get();
+        while (!usedBytes.compareAndSet(used, used-block.getNumBytes())) {
+          used = usedBytes.get();
+        }
+      } else {
+        LOG.info("Successfully cached block " + block.getBlock());
+        cachedBlocks.put(block.getBlock().getBlockId(), block);
+      }
+    }
+  }
+
+  // Stats related methods for FsDatasetMBean
+
+  public long getDnCacheUsed() {
+    return usedBytes.get();
+  }
+
+  public long getDnCacheCapacity() {
+    return maxBytes;
+  }
+}
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetImpl.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetImpl.java
index 2a210b2..010be395 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetImpl.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetImpl.java
@@ -37,6 +37,7 @@
 import javax.management.ObjectName;
 import javax.management.StandardMBean;
 
+import org.apache.commons.io.IOUtils;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.classification.InterfaceAudience;
@@ -170,6 +171,7 @@
   final FsVolumeList volumes;
   final ReplicaMap volumeMap;
   final FsDatasetAsyncDiskService asyncDiskService;
+  final FsDatasetCache cacheManager;
   private final int validVolsRequired;
 
   // Used for synchronizing access to usage stats
@@ -228,6 +230,7 @@
       roots[idx] = storage.getStorageDir(idx).getCurrentDir();
     }
     asyncDiskService = new FsDatasetAsyncDiskService(datanode, roots);
+    cacheManager = new FsDatasetCache(this);
     registerMBean(storage.getStorageID());
   }
 
@@ -288,6 +291,22 @@
   }
 
   /**
+   * Returns the total cache used by the datanode (in bytes).
+   */
+  @Override // FSDatasetMBean
+  public long getDnCacheUsed() {
+    return cacheManager.getDnCacheUsed();
+  }
+
+  /**
+   * Returns the total cache capacity of the datanode (in bytes).
+   */
+  @Override // FSDatasetMBean
+  public long getDnCacheCapacity() {
+    return cacheManager.getDnCacheCapacity();
+  }
+
+  /**
    * Find the block's on-disk length
    */
   @Override // FsDatasetSpi
@@ -534,6 +553,8 @@
   private synchronized ReplicaBeingWritten append(String bpid,
       FinalizedReplica replicaInfo, long newGS, long estimateBlockLen)
       throws IOException {
+    // uncache the block
+    cacheManager.uncacheBlock(bpid, replicaInfo.getBlockId());
     // unlink the finalized replica
     replicaInfo.unlinkBlock(1);
     
@@ -1001,6 +1022,11 @@
     }
   }
 
+  @Override // FsDatasetSpi
+  public List<Long> getCacheReport(String bpid) {
+    return cacheManager.getCachedBlocks(bpid);
+  }
+
   /**
    * Get the list of finalized blocks from in-memory blockmap for a block pool.
    */
@@ -1143,6 +1169,8 @@
         volumeMap.remove(bpid, invalidBlks[i]);
       }
 
+      // Uncache the block synchronously
+      cacheManager.uncacheBlock(bpid, invalidBlks[i].getBlockId());
       // Delete the block asynchronously to make sure we can do it fast enough
       asyncDiskService.deleteAsync(v, f,
           FsDatasetUtil.getMetaFile(f, invalidBlks[i].getGenerationStamp()),
@@ -1153,6 +1181,82 @@
     }
   }
 
+  synchronized boolean validToCache(String bpid, long blockId) {
+    ReplicaInfo info = volumeMap.get(bpid, blockId);
+    if (info == null) {
+      LOG.warn("Failed to cache replica in block pool " + bpid +
+          " with block id " + blockId + ": ReplicaInfo not found.");
+      return false;
+    }
+    FsVolumeImpl volume = (FsVolumeImpl)info.getVolume();
+    if (volume == null) {
+      LOG.warn("Failed to cache block with id " + blockId +
+          ": Volume not found.");
+      return false;
+    }
+    if (info.getState() != ReplicaState.FINALIZED) {
+      LOG.warn("Failed to block with id " + blockId + 
+          ": Replica is not finalized.");
+      return false;
+    }
+    return true;
+  }
+
+  /**
+   * Asynchronously attempts to cache a single block via {@link FsDatasetCache}.
+   */
+  private void cacheBlock(String bpid, long blockId) {
+    ReplicaInfo info;
+    FsVolumeImpl volume;
+    synchronized (this) {
+      if (!validToCache(bpid, blockId)) {
+        return;
+      }
+      info = volumeMap.get(bpid, blockId);
+      volume = (FsVolumeImpl)info.getVolume();
+    }
+    // Try to open block and meta streams
+    FileInputStream blockIn = null;
+    FileInputStream metaIn = null;
+    boolean success = false;
+    ExtendedBlock extBlk =
+        new ExtendedBlock(bpid, blockId,
+            info.getBytesOnDisk(), info.getGenerationStamp());
+    try {
+      blockIn = (FileInputStream)getBlockInputStream(extBlk, 0);
+      metaIn = (FileInputStream)getMetaDataInputStream(extBlk)
+          .getWrappedStream();
+      success = true;
+    } catch (ClassCastException e) {
+      LOG.warn("Failed to cache replica " + extBlk + ": Underlying blocks"
+          + " are not backed by files.", e);
+    } catch (IOException e) {
+      LOG.warn("Failed to cache replica " + extBlk + ": IOException while"
+          + " trying to open block or meta files.", e);
+    }
+    if (!success) {
+      IOUtils.closeQuietly(blockIn);
+      IOUtils.closeQuietly(metaIn);
+      return;
+    }
+    cacheManager.cacheBlock(bpid, extBlk.getLocalBlock(),
+        volume, blockIn, metaIn);
+  }
+
+  @Override // FsDatasetSpi
+  public void cache(String bpid, long[] blockIds) {
+    for (int i=0; i < blockIds.length; i++) {
+      cacheBlock(bpid, blockIds[i]);
+    }
+  }
+
+  @Override // FsDatasetSpi
+  public void uncache(String bpid, long[] blockIds) {
+    for (int i=0; i < blockIds.length; i++) {
+      cacheManager.uncacheBlock(bpid, blockIds[i]);
+    }
+  }
+
   @Override // FsDatasetSpi
   public synchronized boolean contains(final ExtendedBlock block) {
     final long blockId = block.getLocalBlock().getBlockId();
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeImpl.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeImpl.java
index 95cc74e..a2732ca 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeImpl.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeImpl.java
@@ -18,11 +18,17 @@
 package org.apache.hadoop.hdfs.server.datanode.fsdataset.impl;
 
 import java.io.File;
+import java.io.FileInputStream;
 import java.io.IOException;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Set;
+import java.util.concurrent.Executor;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
 
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.conf.Configuration;
@@ -34,6 +40,8 @@
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
 import org.apache.hadoop.util.DiskChecker.DiskErrorException;
 
+import com.google.common.util.concurrent.ThreadFactoryBuilder;
+
 /**
  * The underlying volume used to store replica.
  * 
@@ -48,6 +56,13 @@
   private final File currentDir;    // <StorageDirectory>/current
   private final DF usage;           
   private final long reserved;
+  /**
+   * Per-volume worker pool that processes new blocks to cache.
+   * The maximum number of workers per volume is bounded (configurable via
+   * dfs.datanode.fsdatasetcache.max.threads.per.volume) to limit resource
+   * contention.
+   */
+  private final ThreadPoolExecutor cacheExecutor;
   
   FsVolumeImpl(FsDatasetImpl dataset, String storageID, File currentDir,
       Configuration conf) throws IOException {
@@ -59,6 +74,20 @@
     this.currentDir = currentDir; 
     File parent = currentDir.getParentFile();
     this.usage = new DF(parent, conf);
+    final int maxNumThreads = dataset.datanode.getConf().getInt(
+        DFSConfigKeys.DFS_DATANODE_FSDATASETCACHE_MAX_THREADS_PER_VOLUME_KEY,
+        DFSConfigKeys.DFS_DATANODE_FSDATASETCACHE_MAX_THREADS_PER_VOLUME_DEFAULT
+        );
+    ThreadFactory workerFactory = new ThreadFactoryBuilder()
+        .setDaemon(true)
+        .setNameFormat("FsVolumeImplWorker-" + parent.toString() + "-%d")
+        .build();
+    cacheExecutor = new ThreadPoolExecutor(
+        1, maxNumThreads,
+        60, TimeUnit.SECONDS,
+        new LinkedBlockingQueue<Runnable>(),
+        workerFactory);
+    cacheExecutor.allowCoreThreadTimeOut(true);
   }
   
   File getCurrentDir() {
@@ -166,7 +195,11 @@
   File addBlock(String bpid, Block b, File f) throws IOException {
     return getBlockPoolSlice(bpid).addBlock(b, f);
   }
-    
+
+  Executor getExecutor() {
+    return cacheExecutor;
+  }
+
   void checkDirs() throws DiskErrorException {
     // TODO:FEDERATION valid synchronization
     for(BlockPoolSlice s : bpSlices.values()) {
@@ -210,6 +243,7 @@
   }
 
   void shutdown() {
+    cacheExecutor.shutdown();
     Set<Entry<String, BlockPoolSlice>> set = bpSlices.entrySet();
     for (Entry<String, BlockPoolSlice> entry : set) {
       entry.getValue().shutdown();
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/MappableBlock.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/MappableBlock.java
new file mode 100644
index 0000000..a2a9e6c
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/MappableBlock.java
@@ -0,0 +1,249 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.hdfs.server.datanode.fsdataset.impl;
+
+import java.io.BufferedInputStream;
+import java.io.Closeable;
+import java.io.DataInputStream;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.MappedByteBuffer;
+import java.nio.channels.FileChannel;
+import java.nio.channels.FileChannel.MapMode;
+
+import org.apache.commons.io.IOUtils;
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+import org.apache.hadoop.fs.ChecksumException;
+import org.apache.hadoop.hdfs.protocol.Block;
+import org.apache.hadoop.hdfs.server.datanode.BlockMetadataHeader;
+import org.apache.hadoop.io.nativeio.NativeIO;
+import org.apache.hadoop.util.DataChecksum;
+
+import com.google.common.base.Preconditions;
+
+/**
+ * Low-level wrapper for a Block and its backing files that provides mmap,
+ * mlock, and checksum verification operations.
+ * 
+ * This could be a private class of FsDatasetCache, not meant for other users.
+ */
+@InterfaceAudience.Private
+@InterfaceStability.Unstable
+class MappableBlock implements Closeable {
+
+  private final String bpid;
+  private final Block block;
+  private final FsVolumeImpl volume;
+
+  private final FileInputStream blockIn;
+  private final FileInputStream metaIn;
+  private final FileChannel blockChannel;
+  private final FileChannel metaChannel;
+  private final long blockSize;
+
+  private boolean isMapped;
+  private boolean isLocked;
+  private boolean isChecksummed;
+
+  private MappedByteBuffer blockMapped = null;
+
+  public MappableBlock(String bpid, Block blk, FsVolumeImpl volume,
+      FileInputStream blockIn, FileInputStream metaIn) throws IOException {
+    this.bpid = bpid;
+    this.block = blk;
+    this.volume = volume;
+
+    this.blockIn = blockIn;
+    this.metaIn = metaIn;
+    this.blockChannel = blockIn.getChannel();
+    this.metaChannel = metaIn.getChannel();
+    this.blockSize = blockChannel.size();
+
+    this.isMapped = false;
+    this.isLocked = false;
+    this.isChecksummed = false;
+  }
+
+  public String getBlockPoolId() {
+    return bpid;
+  }
+
+  public Block getBlock() {
+    return block;
+  }
+
+  public FsVolumeImpl getVolume() {
+    return volume;
+  }
+
+  public boolean isMapped() {
+    return isMapped;
+  }
+
+  public boolean isLocked() {
+    return isLocked;
+  }
+
+  public boolean isChecksummed() {
+    return isChecksummed;
+  }
+
+  /**
+   * Returns the number of bytes on disk for the block file
+   */
+  public long getNumBytes() {
+    return blockSize;
+  }
+
+  /**
+   * Maps the block into memory. See mmap(2).
+   */
+  public void map() throws IOException {
+    if (isMapped) {
+      return;
+    }
+    blockMapped = blockChannel.map(MapMode.READ_ONLY, 0, blockSize);
+    isMapped = true;
+  }
+
+  /**
+   * Unmaps the block from memory. See munmap(2).
+   */
+  public void unmap() {
+    if (!isMapped) {
+      return;
+    }
+    if (blockMapped instanceof sun.nio.ch.DirectBuffer) {
+      sun.misc.Cleaner cleaner =
+          ((sun.nio.ch.DirectBuffer)blockMapped).cleaner();
+      cleaner.clean();
+    }
+    isMapped = false;
+    isLocked = false;
+    isChecksummed = false;
+  }
+
+  /**
+   * Locks the block into memory. This prevents the block from being paged out.
+   * See mlock(2).
+   */
+  public void lock() throws IOException {
+    Preconditions.checkArgument(isMapped,
+        "Block must be mapped before it can be locked!");
+    if (isLocked) {
+      return;
+    }
+    NativeIO.POSIX.mlock(blockMapped, blockSize);
+    isLocked = true;
+  }
+
+  /**
+   * Unlocks the block from memory, allowing it to be paged out. See munlock(2).
+   */
+  public void unlock() throws IOException {
+    if (!isLocked || !isMapped) {
+      return;
+    }
+    NativeIO.POSIX.munlock(blockMapped, blockSize);
+    isLocked = false;
+    isChecksummed = false;
+  }
+
+  /**
+   * Reads bytes into a buffer until EOF or the buffer's limit is reached
+   */
+  private int fillBuffer(FileChannel channel, ByteBuffer buf)
+      throws IOException {
+    int bytesRead = channel.read(buf);
+    if (bytesRead < 0) {
+      //EOF
+      return bytesRead;
+    }
+    while (buf.remaining() > 0) {
+      int n = channel.read(buf);
+      if (n < 0) {
+        //EOF
+        return bytesRead;
+      }
+      bytesRead += n;
+    }
+    return bytesRead;
+  }
+
+  /**
+   * Verifies the block's checksum. This is an I/O intensive operation.
+   * @return if the block was successfully checksummed.
+   */
+  public void verifyChecksum() throws IOException, ChecksumException {
+    Preconditions.checkArgument(isLocked && isMapped,
+        "Block must be mapped and locked before checksum verification!");
+    // skip if checksum has already been successfully verified
+    if (isChecksummed) {
+      return;
+    }
+    // Verify the checksum from the block's meta file
+    // Get the DataChecksum from the meta file header
+    metaChannel.position(0);
+    BlockMetadataHeader header =
+        BlockMetadataHeader.readHeader(new DataInputStream(
+            new BufferedInputStream(metaIn, BlockMetadataHeader
+                .getHeaderSize())));
+    DataChecksum checksum = header.getChecksum();
+    final int bytesPerChecksum = checksum.getBytesPerChecksum();
+    final int checksumSize = checksum.getChecksumSize();
+    final int numChunks = (8*1024*1024) / bytesPerChecksum;
+    ByteBuffer blockBuf = ByteBuffer.allocate(numChunks*bytesPerChecksum);
+    ByteBuffer checksumBuf = ByteBuffer.allocate(numChunks*checksumSize);
+    // Verify the checksum
+    int bytesVerified = 0;
+    while (bytesVerified < blockChannel.size()) {
+      Preconditions.checkState(bytesVerified % bytesPerChecksum == 0,
+          "Unexpected partial chunk before EOF");
+      assert bytesVerified % bytesPerChecksum == 0;
+      int bytesRead = fillBuffer(blockChannel, blockBuf);
+      if (bytesRead == -1) {
+        throw new IOException("Premature EOF");
+      }
+      blockBuf.flip();
+      // Number of read chunks, including partial chunk at end
+      int chunks = (bytesRead+bytesPerChecksum-1) / bytesPerChecksum;
+      checksumBuf.limit(chunks*checksumSize);
+      fillBuffer(metaChannel, checksumBuf);
+      checksumBuf.flip();
+      checksum.verifyChunkedSums(blockBuf, checksumBuf, block.getBlockName(),
+          bytesVerified);
+      // Success
+      bytesVerified += bytesRead;
+      blockBuf.clear();
+      checksumBuf.clear();
+    }
+    isChecksummed = true;
+    // Can close the backing file since everything is safely in memory
+    blockChannel.close();
+  }
+
+  @Override
+  public void close() {
+    unmap();
+    IOUtils.closeQuietly(blockIn);
+    IOUtils.closeQuietly(metaIn);
+  }
+}
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/metrics/DataNodeMetrics.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/metrics/DataNodeMetrics.java
index a9237c5..ffdb8e7 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/metrics/DataNodeMetrics.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/metrics/DataNodeMetrics.java
@@ -57,6 +57,8 @@
   @Metric MutableCounterLong blocksRemoved;
   @Metric MutableCounterLong blocksVerified;
   @Metric MutableCounterLong blockVerificationFailures;
+  @Metric MutableCounterLong blocksCached;
+  @Metric MutableCounterLong blocksUncached;
   @Metric MutableCounterLong readsFromLocalClient;
   @Metric MutableCounterLong readsFromRemoteClient;
   @Metric MutableCounterLong writesFromLocalClient;
@@ -74,6 +76,7 @@
   @Metric MutableRate replaceBlockOp;
   @Metric MutableRate heartbeats;
   @Metric MutableRate blockReports;
+  @Metric MutableRate cacheReports;
   @Metric MutableRate packetAckRoundTripTimeNanos;
   MutableQuantiles[] packetAckRoundTripTimeNanosQuantiles;
   
@@ -151,6 +154,10 @@
     blockReports.add(latency);
   }
 
+  public void addCacheReport(long latency) {
+    cacheReports.add(latency);
+  }
+
   public void incrBlocksReplicated(int delta) {
     blocksReplicated.incr(delta);
   }
@@ -175,6 +182,15 @@
     blocksVerified.incr();
   }
 
+
+  public void incrBlocksCached(int delta) {
+    blocksCached.incr(delta);
+  }
+
+  public void incrBlocksUncached(int delta) {
+    blocksUncached.incr(delta);
+  }
+
   public void addReadBlockOp(long latency) {
     readBlockOp.add(latency);
   }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/metrics/FSDatasetMBean.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/metrics/FSDatasetMBean.java
index 2ff601d..82757d0 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/metrics/FSDatasetMBean.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/metrics/FSDatasetMBean.java
@@ -77,4 +77,14 @@
    * @return The number of failed volumes in the datanode.
    */
   public int getNumFailedVolumes();
+
+  /**
+   * Returns the total cache used by the datanode (in bytes).
+   */
+  public long getDnCacheUsed();
+
+  /**
+   * Returns the total cache capacity of the datanode (in bytes).
+   */
+  public long getDnCacheCapacity();
 }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/CacheManager.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/CacheManager.java
new file mode 100644
index 0000000..bda729c
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/CacheManager.java
@@ -0,0 +1,743 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.server.namenode;
+
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_LIST_CACHE_POOLS_NUM_RESPONSES;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_LIST_CACHE_POOLS_NUM_RESPONSES_DEFAULT;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_LIST_CACHE_DESCRIPTORS_NUM_RESPONSES;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_CACHING_ENABLED_KEY;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_CACHING_ENABLED_DEFAULT;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_LIST_CACHE_DESCRIPTORS_NUM_RESPONSES_DEFAULT;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_PATH_BASED_CACHE_REFRESH_INTERVAL_MS;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_PATH_BASED_CACHE_REFRESH_INTERVAL_MS_DEFAULT;
+
+import java.io.Closeable;
+import java.io.DataInput;
+import java.io.DataOutput;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map.Entry;
+import java.util.SortedMap;
+import java.util.TreeMap;
+
+import org.apache.commons.io.IOUtils;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.BatchedRemoteIterator.BatchedListEntries;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.fs.permission.FsAction;
+import org.apache.hadoop.hdfs.DFSUtil;
+import org.apache.hadoop.hdfs.protocol.Block;
+import org.apache.hadoop.hdfs.protocol.BlockListAsLongs;
+import org.apache.hadoop.hdfs.protocol.BlockListAsLongs.BlockReportIterator;
+import org.apache.hadoop.hdfs.protocol.CachePoolInfo;
+import org.apache.hadoop.hdfs.protocol.DatanodeID;
+import org.apache.hadoop.hdfs.protocol.LocatedBlock;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDirective;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDescriptor;
+import org.apache.hadoop.hdfs.protocol.AddPathBasedCacheDirectiveException.InvalidPoolNameError;
+import org.apache.hadoop.hdfs.protocol.AddPathBasedCacheDirectiveException.UnexpectedAddPathBasedCacheDirectiveException;
+import org.apache.hadoop.hdfs.protocol.AddPathBasedCacheDirectiveException.PoolWritePermissionDeniedError;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheEntry;
+import org.apache.hadoop.hdfs.protocol.RemovePathBasedCacheDescriptorException.InvalidIdException;
+import org.apache.hadoop.hdfs.protocol.RemovePathBasedCacheDescriptorException.NoSuchIdException;
+import org.apache.hadoop.hdfs.protocol.RemovePathBasedCacheDescriptorException.UnexpectedRemovePathBasedCacheDescriptorException;
+import org.apache.hadoop.hdfs.protocol.RemovePathBasedCacheDescriptorException.RemovePermissionDeniedException;
+import org.apache.hadoop.hdfs.server.blockmanagement.BlockInfo;
+import org.apache.hadoop.hdfs.server.blockmanagement.BlockManager;
+import org.apache.hadoop.hdfs.server.blockmanagement.CacheReplicationMonitor;
+import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor;
+import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor.CachedBlocksList;
+import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor.CachedBlocksList.Type;
+import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.ReplicaState;
+import org.apache.hadoop.hdfs.server.namenode.metrics.NameNodeMetrics;
+import org.apache.hadoop.hdfs.server.namenode.startupprogress.Phase;
+import org.apache.hadoop.hdfs.server.namenode.startupprogress.StartupProgress;
+import org.apache.hadoop.hdfs.server.namenode.startupprogress.StartupProgress.Counter;
+import org.apache.hadoop.hdfs.server.namenode.startupprogress.Step;
+import org.apache.hadoop.hdfs.server.namenode.startupprogress.StepType;
+import org.apache.hadoop.io.Text;
+import org.apache.hadoop.util.GSet;
+import org.apache.hadoop.util.LightWeightGSet;
+import org.apache.hadoop.util.Time;
+
+import com.google.common.annotations.VisibleForTesting;
+
+/**
+ * The Cache Manager handles caching on DataNodes.
+ *
+ * This class is instantiated by the FSNamesystem when caching is enabled.
+ * It maintains the mapping of cached blocks to datanodes via processing
+ * datanode cache reports. Based on these reports and addition and removal of
+ * caching directives, we will schedule caching and uncaching work.
+ */
+@InterfaceAudience.LimitedPrivate({"HDFS"})
+public final class CacheManager {
+  public static final Log LOG = LogFactory.getLog(CacheManager.class);
+
+  // TODO: add pending / underCached / schedule cached blocks stats.
+
+  /**
+   * The FSNamesystem that contains this CacheManager.
+   */
+  private final FSNamesystem namesystem;
+
+  /**
+   * The BlockManager associated with the FSN that owns this CacheManager.
+   */
+  private final BlockManager blockManager;
+
+  /**
+   * Cache entries, sorted by ID.
+   *
+   * listPathBasedCacheDescriptors relies on the ordering of elements in this map 
+   * to track what has already been listed by the client.
+   */
+  private final TreeMap<Long, PathBasedCacheEntry> entriesById =
+      new TreeMap<Long, PathBasedCacheEntry>();
+
+  /**
+   * The entry ID to use for a new entry.  Entry IDs always increase, and are
+   * never reused.
+   */
+  private long nextEntryId;
+
+  /**
+   * Cache entries, sorted by path
+   */
+  private final TreeMap<String, List<PathBasedCacheEntry>> entriesByPath =
+      new TreeMap<String, List<PathBasedCacheEntry>>();
+
+  /**
+   * Cache pools, sorted by name.
+   */
+  private final TreeMap<String, CachePool> cachePools =
+      new TreeMap<String, CachePool>();
+
+  /**
+   * Maximum number of cache pools to list in one operation.
+   */
+  private final int maxListCachePoolsResponses;
+
+  /**
+   * Maximum number of cache pool directives to list in one operation.
+   */
+  private final int maxListCacheDescriptorsResponses;
+
+  /**
+   * Interval between scans in milliseconds.
+   */
+  private final long scanIntervalMs;
+
+  /**
+   * Whether caching is enabled.
+   *
+   * If caching is disabled, we will not process cache reports or store
+   * information about what is cached where.  We also do not start the
+   * CacheReplicationMonitor thread.  This will save resources, but provide
+   * less functionality.
+   *     
+   * Even when caching is disabled, we still store path-based cache
+   * information.  This information is stored in the edit log and fsimage.  We
+   * don't want to lose it just because a configuration setting was turned off.
+   * However, we will not act on this information if caching is disabled.
+   */
+  private final boolean enabled;
+
+  /**
+   * Whether the CacheManager is active.
+   * 
+   * When the CacheManager is active, it tells the DataNodes what to cache
+   * and uncache.  The CacheManager cannot become active if enabled = false.
+   */
+  private boolean active = false;
+
+  /**
+   * All cached blocks.
+   */
+  private final GSet<CachedBlock, CachedBlock> cachedBlocks;
+
+  /**
+   * The CacheReplicationMonitor.
+   */
+  private CacheReplicationMonitor monitor;
+
+  CacheManager(FSNamesystem namesystem, Configuration conf,
+      BlockManager blockManager) {
+    this.namesystem = namesystem;
+    this.blockManager = blockManager;
+    this.nextEntryId = 1;
+    this.maxListCachePoolsResponses = conf.getInt(
+        DFS_NAMENODE_LIST_CACHE_POOLS_NUM_RESPONSES,
+        DFS_NAMENODE_LIST_CACHE_POOLS_NUM_RESPONSES_DEFAULT);
+    this.maxListCacheDescriptorsResponses = conf.getInt(
+        DFS_NAMENODE_LIST_CACHE_DESCRIPTORS_NUM_RESPONSES,
+        DFS_NAMENODE_LIST_CACHE_DESCRIPTORS_NUM_RESPONSES_DEFAULT);
+    scanIntervalMs = conf.getLong(
+        DFS_NAMENODE_PATH_BASED_CACHE_REFRESH_INTERVAL_MS,
+        DFS_NAMENODE_PATH_BASED_CACHE_REFRESH_INTERVAL_MS_DEFAULT);
+    this.enabled = conf.getBoolean(DFS_NAMENODE_CACHING_ENABLED_KEY,
+        DFS_NAMENODE_CACHING_ENABLED_DEFAULT);
+    this.cachedBlocks = !enabled ? null :
+        new LightWeightGSet<CachedBlock, CachedBlock>(
+            LightWeightGSet.computeCapacity(0.25, "cachedBlocks"));
+  }
+
+  /**
+   * Activate the cache manager.
+   * 
+   * When the cache manager is active, tell the datanodes where to cache files.
+   */
+  public void activate() {
+    assert namesystem.hasWriteLock();
+    if (enabled && (!active)) {
+      LOG.info("Activating CacheManager.  " +
+          "Starting replication monitor thread...");
+      active = true;
+      monitor = new CacheReplicationMonitor(namesystem, this,
+         scanIntervalMs);
+      monitor.start();
+    }
+  }
+
+  /**
+   * Deactivate the cache manager.
+   * 
+   * When the cache manager is inactive, it does not tell the datanodes where to
+   * cache files.
+   */
+  public void deactivate() {
+    assert namesystem.hasWriteLock();
+    if (active) {
+      LOG.info("Deactivating CacheManager.  " +
+          "stopping CacheReplicationMonitor thread...");
+      active = false;
+      IOUtils.closeQuietly(monitor);
+      monitor = null;
+      LOG.info("CacheReplicationMonitor thread stopped and deactivated.");
+    }
+  }
+
+  /**
+   * Return true only if the cache manager is active.
+   * Must be called under the FSN read or write lock.
+   */
+  public boolean isActive() {
+    return active;
+  }
+
+  public TreeMap<Long, PathBasedCacheEntry> getEntriesById() {
+    assert namesystem.hasReadOrWriteLock();
+    return entriesById;
+  }
+  
+  @VisibleForTesting
+  public GSet<CachedBlock, CachedBlock> getCachedBlocks() {
+    assert namesystem.hasReadOrWriteLock();
+    return cachedBlocks;
+  }
+
+  private long getNextEntryId() throws IOException {
+    assert namesystem.hasWriteLock();
+    if (nextEntryId == Long.MAX_VALUE) {
+      throw new IOException("No more available IDs");
+    }
+    return nextEntryId++;
+  }
+
+  public PathBasedCacheDescriptor addDirective(
+      PathBasedCacheDirective directive, FSPermissionChecker pc)
+      throws IOException {
+    assert namesystem.hasWriteLock();
+    CachePool pool = cachePools.get(directive.getPool());
+    if (pool == null) {
+      LOG.info("addDirective " + directive + ": pool not found.");
+      throw new InvalidPoolNameError(directive);
+    }
+    if ((pc != null) && (!pc.checkPermission(pool, FsAction.WRITE))) {
+      LOG.info("addDirective " + directive + ": write permission denied.");
+      throw new PoolWritePermissionDeniedError(directive);
+    }
+    try {
+      directive.validate();
+    } catch (IOException ioe) {
+      LOG.info("addDirective " + directive + ": validation failed: "
+          + ioe.getClass().getName() + ": " + ioe.getMessage());
+      throw ioe;
+    }
+    
+    // Add a new entry with the next available ID.
+    PathBasedCacheEntry entry;
+    try {
+      entry = new PathBasedCacheEntry(getNextEntryId(),
+          directive.getPath().toUri().getPath(),
+          directive.getReplication(), pool);
+    } catch (IOException ioe) {
+      throw new UnexpectedAddPathBasedCacheDirectiveException(directive);
+    }
+    LOG.info("addDirective " + directive + ": added cache directive "
+        + directive);
+
+    // Success!
+    // First, add it to the various maps
+    entriesById.put(entry.getEntryId(), entry);
+    String path = directive.getPath().toUri().getPath();
+    List<PathBasedCacheEntry> entryList = entriesByPath.get(path);
+    if (entryList == null) {
+      entryList = new ArrayList<PathBasedCacheEntry>(1);
+      entriesByPath.put(path, entryList);
+    }
+    entryList.add(entry);
+    if (monitor != null) {
+      monitor.kick();
+    }
+    return entry.getDescriptor();
+  }
+
+  public void removeDescriptor(long id, FSPermissionChecker pc)
+      throws IOException {
+    assert namesystem.hasWriteLock();
+    // Check for invalid IDs.
+    if (id <= 0) {
+      LOG.info("removeDescriptor " + id + ": invalid non-positive " +
+          "descriptor ID.");
+      throw new InvalidIdException(id);
+    }
+    // Find the entry.
+    PathBasedCacheEntry existing = entriesById.get(id);
+    if (existing == null) {
+      LOG.info("removeDescriptor " + id + ": entry not found.");
+      throw new NoSuchIdException(id);
+    }
+    CachePool pool = cachePools.get(existing.getDescriptor().getPool());
+    if (pool == null) {
+      LOG.info("removeDescriptor " + id + ": pool not found for directive " +
+        existing.getDescriptor());
+      throw new UnexpectedRemovePathBasedCacheDescriptorException(id);
+    }
+    if ((pc != null) && (!pc.checkPermission(pool, FsAction.WRITE))) {
+      LOG.info("removeDescriptor " + id + ": write permission denied to " +
+          "pool " + pool + " for entry " + existing);
+      throw new RemovePermissionDeniedException(id);
+    }
+    
+    // Remove the corresponding entry in entriesByPath.
+    String path = existing.getDescriptor().getPath().toUri().getPath();
+    List<PathBasedCacheEntry> entries = entriesByPath.get(path);
+    if (entries == null || !entries.remove(existing)) {
+      throw new UnexpectedRemovePathBasedCacheDescriptorException(id);
+    }
+    if (entries.size() == 0) {
+      entriesByPath.remove(path);
+    }
+    entriesById.remove(id);
+    if (monitor != null) {
+      monitor.kick();
+    }
+    LOG.info("removeDescriptor successful for PathCacheEntry id " + id);
+  }
+
+  public BatchedListEntries<PathBasedCacheDescriptor> 
+        listPathBasedCacheDescriptors(long prevId, String filterPool,
+            String filterPath, FSPermissionChecker pc) throws IOException {
+    assert namesystem.hasReadOrWriteLock();
+    final int NUM_PRE_ALLOCATED_ENTRIES = 16;
+    if (filterPath != null) {
+      if (!DFSUtil.isValidName(filterPath)) {
+        throw new IOException("invalid path name '" + filterPath + "'");
+      }
+    }
+    ArrayList<PathBasedCacheDescriptor> replies =
+        new ArrayList<PathBasedCacheDescriptor>(NUM_PRE_ALLOCATED_ENTRIES);
+    int numReplies = 0;
+    SortedMap<Long, PathBasedCacheEntry> tailMap = entriesById.tailMap(prevId + 1);
+    for (Entry<Long, PathBasedCacheEntry> cur : tailMap.entrySet()) {
+      if (numReplies >= maxListCacheDescriptorsResponses) {
+        return new BatchedListEntries<PathBasedCacheDescriptor>(replies, true);
+      }
+      PathBasedCacheEntry curEntry = cur.getValue();
+      PathBasedCacheDirective directive = cur.getValue().getDescriptor();
+      if (filterPool != null && 
+          !directive.getPool().equals(filterPool)) {
+        continue;
+      }
+      if (filterPath != null &&
+          !directive.getPath().toUri().getPath().equals(filterPath)) {
+        continue;
+      }
+      if (pc.checkPermission(curEntry.getPool(), FsAction.READ)) {
+        replies.add(cur.getValue().getDescriptor());
+        numReplies++;
+      }
+    }
+    return new BatchedListEntries<PathBasedCacheDescriptor>(replies, false);
+  }
+
+  /**
+   * Create a cache pool.
+   * 
+   * Only the superuser should be able to call this function.
+   *
+   * @param info    The info for the cache pool to create.
+   * @return        Information about the cache pool we created.
+   */
+  public CachePoolInfo addCachePool(CachePoolInfo info)
+      throws IOException {
+    assert namesystem.hasWriteLock();
+    CachePoolInfo.validate(info);
+    String poolName = info.getPoolName();
+    CachePool pool = cachePools.get(poolName);
+    if (pool != null) {
+      throw new IOException("cache pool " + poolName + " already exists.");
+    }
+    pool = CachePool.createFromInfoAndDefaults(info);
+    cachePools.put(pool.getPoolName(), pool);
+    LOG.info("created new cache pool " + pool);
+    return pool.getInfo(true);
+  }
+
+  /**
+   * Modify a cache pool.
+   * 
+   * Only the superuser should be able to call this function.
+   *
+   * @param info
+   *          The info for the cache pool to modify.
+   */
+  public void modifyCachePool(CachePoolInfo info)
+      throws IOException {
+    assert namesystem.hasWriteLock();
+    CachePoolInfo.validate(info);
+    String poolName = info.getPoolName();
+    CachePool pool = cachePools.get(poolName);
+    if (pool == null) {
+      throw new IOException("cache pool " + poolName + " does not exist.");
+    }
+    StringBuilder bld = new StringBuilder();
+    String prefix = "";
+    if (info.getOwnerName() != null) {
+      pool.setOwnerName(info.getOwnerName());
+      bld.append(prefix).
+        append("set owner to ").append(info.getOwnerName());
+      prefix = "; ";
+    }
+    if (info.getGroupName() != null) {
+      pool.setGroupName(info.getGroupName());
+      bld.append(prefix).
+        append("set group to ").append(info.getGroupName());
+      prefix = "; ";
+    }
+    if (info.getMode() != null) {
+      pool.setMode(info.getMode());
+      bld.append(prefix).append("set mode to " + info.getMode());
+      prefix = "; ";
+    }
+    if (info.getWeight() != null) {
+      pool.setWeight(info.getWeight());
+      bld.append(prefix).
+        append("set weight to ").append(info.getWeight());
+      prefix = "; ";
+    }
+    if (prefix.isEmpty()) {
+      bld.append("no changes.");
+    }
+    LOG.info("modified " + poolName + "; " + bld.toString());
+  }
+
+  /**
+   * Remove a cache pool.
+   * 
+   * Only the superuser should be able to call this function.
+   *
+   * @param poolName
+   *          The name for the cache pool to remove.
+   */
+  public void removeCachePool(String poolName)
+      throws IOException {
+    assert namesystem.hasWriteLock();
+    CachePoolInfo.validateName(poolName);
+    CachePool pool = cachePools.remove(poolName);
+    if (pool == null) {
+      throw new IOException("can't remove non-existent cache pool " + poolName);
+    }
+    
+    // Remove entries using this pool
+    // TODO: could optimize this somewhat to avoid the need to iterate
+    // over all entries in entriesById
+    Iterator<Entry<Long, PathBasedCacheEntry>> iter = 
+        entriesById.entrySet().iterator();
+    while (iter.hasNext()) {
+      Entry<Long, PathBasedCacheEntry> entry = iter.next();
+      if (entry.getValue().getPool() == pool) {
+        entriesByPath.remove(entry.getValue().getPath());
+        iter.remove();
+      }
+    }
+    if (monitor != null) {
+      monitor.kick();
+    }
+  }
+
+  public BatchedListEntries<CachePoolInfo>
+      listCachePools(FSPermissionChecker pc, String prevKey) {
+    assert namesystem.hasReadOrWriteLock();
+    final int NUM_PRE_ALLOCATED_ENTRIES = 16;
+    ArrayList<CachePoolInfo> results = 
+        new ArrayList<CachePoolInfo>(NUM_PRE_ALLOCATED_ENTRIES);
+    SortedMap<String, CachePool> tailMap = cachePools.tailMap(prevKey, false);
+    int numListed = 0;
+    for (Entry<String, CachePool> cur : tailMap.entrySet()) {
+      if (numListed++ >= maxListCachePoolsResponses) {
+        return new BatchedListEntries<CachePoolInfo>(results, true);
+      }
+      if (pc == null) {
+        results.add(cur.getValue().getInfo(true));
+      } else {
+        results.add(cur.getValue().getInfo(pc));
+      }
+    }
+    return new BatchedListEntries<CachePoolInfo>(results, false);
+  }
+
+  public void setCachedLocations(LocatedBlock block) {
+    if (!enabled) {
+      return;
+    }
+    CachedBlock cachedBlock =
+        new CachedBlock(block.getBlock().getBlockId(),
+            (short)0, false);
+    cachedBlock = cachedBlocks.get(cachedBlock);
+    if (cachedBlock == null) {
+      return;
+    }
+    List<DatanodeDescriptor> datanodes = cachedBlock.getDatanodes(Type.CACHED);
+    for (DatanodeDescriptor datanode : datanodes) {
+      block.addCachedLoc(datanode);
+    }
+  }
+
+  public final void processCacheReport(final DatanodeID datanodeID,
+      final List<Long> blockIds) throws IOException {
+    if (!enabled) {
+      LOG.info("Ignoring cache report from " + datanodeID +
+          " because " + DFS_NAMENODE_CACHING_ENABLED_KEY + " = false. " +
+          "number of blocks: " + blockIds.size());
+      return;
+    }
+    namesystem.writeLock();
+    final long startTime = Time.monotonicNow();
+    final long endTime;
+    try {
+      final DatanodeDescriptor datanode = 
+          blockManager.getDatanodeManager().getDatanode(datanodeID);
+      if (datanode == null || !datanode.isAlive) {
+        throw new IOException(
+            "processCacheReport from dead or unregistered datanode: " + datanode);
+      }
+      processCacheReportImpl(datanode, blockIds);
+    } finally {
+      endTime = Time.monotonicNow();
+      namesystem.writeUnlock();
+    }
+
+    // Log the block report processing stats from Namenode perspective
+    final NameNodeMetrics metrics = NameNode.getNameNodeMetrics();
+    if (metrics != null) {
+      metrics.addCacheBlockReport((int) (endTime - startTime));
+    }
+    LOG.info("Processed cache report from "
+        + datanodeID + ", blocks: " + blockIds.size()
+        + ", processing time: " + (endTime - startTime) + " msecs");
+  }
+
+  private void processCacheReportImpl(final DatanodeDescriptor datanode,
+      final List<Long> blockIds) {
+    CachedBlocksList cached = datanode.getCached();
+    cached.clear();
+    for (Iterator<Long> iter = blockIds.iterator(); iter.hasNext(); ) {
+      Block block = new Block(iter.next());
+      BlockInfo blockInfo = blockManager.getStoredBlock(block);
+      if (blockInfo.getGenerationStamp() < block.getGenerationStamp()) {
+        // The NameNode will eventually remove or update the out-of-date block.
+        // Until then, we pretend that it isn't cached.
+        LOG.warn("Genstamp in cache report disagrees with our genstamp for " +
+          block + ": expected genstamp " + blockInfo.getGenerationStamp());
+        continue;
+      }
+      if (!blockInfo.isComplete()) {
+        LOG.warn("Ignoring block id " + block.getBlockId() + ", because " +
+            "it is in not complete yet.  It is in state " + 
+            blockInfo.getBlockUCState());
+        continue;
+      }
+      Collection<DatanodeDescriptor> corruptReplicas =
+          blockManager.getCorruptReplicas(blockInfo);
+      if ((corruptReplicas != null) && corruptReplicas.contains(datanode)) {
+        // The NameNode will eventually remove or update the corrupt block.
+        // Until then, we pretend that it isn't cached.
+        LOG.warn("Ignoring cached replica on " + datanode + " of " + block +
+            " because it is corrupt.");
+        continue;
+      }
+      CachedBlock cachedBlock =
+          new CachedBlock(block.getBlockId(), (short)0, false);
+      CachedBlock prevCachedBlock = cachedBlocks.get(cachedBlock);
+      // Use the existing CachedBlock if it's present; otherwise,
+      // insert a new one.
+      if (prevCachedBlock != null) {
+        cachedBlock = prevCachedBlock;
+      } else {
+        cachedBlocks.put(cachedBlock);
+      }
+      if (!cachedBlock.isPresent(datanode.getCached())) {
+        datanode.getCached().add(cachedBlock);
+      }
+      if (cachedBlock.isPresent(datanode.getPendingCached())) {
+        datanode.getPendingCached().remove(cachedBlock);
+      }
+    }
+  }
+
+  /**
+   * Saves the current state of the CacheManager to the DataOutput. Used
+   * to persist CacheManager state in the FSImage.
+   * @param out DataOutput to persist state
+   * @param sdPath path of the storage directory
+   * @throws IOException
+   */
+  public void saveState(DataOutput out, String sdPath)
+      throws IOException {
+    out.writeLong(nextEntryId);
+    savePools(out, sdPath);
+    saveEntries(out, sdPath);
+  }
+
+  /**
+   * Reloads CacheManager state from the passed DataInput. Used during namenode
+   * startup to restore CacheManager state from an FSImage.
+   * @param in DataInput from which to restore state
+   * @throws IOException
+   */
+  public void loadState(DataInput in) throws IOException {
+    nextEntryId = in.readLong();
+    // pools need to be loaded first since entries point to their parent pool
+    loadPools(in);
+    loadEntries(in);
+  }
+
+  /**
+   * Save cache pools to fsimage
+   */
+  private void savePools(DataOutput out,
+      String sdPath) throws IOException {
+    StartupProgress prog = NameNode.getStartupProgress();
+    Step step = new Step(StepType.CACHE_POOLS, sdPath);
+    prog.beginStep(Phase.SAVING_CHECKPOINT, step);
+    prog.setTotal(Phase.SAVING_CHECKPOINT, step, cachePools.size());
+    Counter counter = prog.getCounter(Phase.SAVING_CHECKPOINT, step);
+    out.writeInt(cachePools.size());
+    for (CachePool pool: cachePools.values()) {
+      pool.getInfo(true).writeTo(out);
+      counter.increment();
+    }
+    prog.endStep(Phase.SAVING_CHECKPOINT, step);
+  }
+
+  /*
+   * Save cache entries to fsimage
+   */
+  private void saveEntries(DataOutput out, String sdPath)
+      throws IOException {
+    StartupProgress prog = NameNode.getStartupProgress();
+    Step step = new Step(StepType.CACHE_ENTRIES, sdPath);
+    prog.beginStep(Phase.SAVING_CHECKPOINT, step);
+    prog.setTotal(Phase.SAVING_CHECKPOINT, step, entriesById.size());
+    Counter counter = prog.getCounter(Phase.SAVING_CHECKPOINT, step);
+    out.writeInt(entriesById.size());
+    for (PathBasedCacheEntry entry: entriesById.values()) {
+      out.writeLong(entry.getEntryId());
+      Text.writeString(out, entry.getPath());
+      out.writeShort(entry.getReplication());
+      Text.writeString(out, entry.getPool().getPoolName());
+      counter.increment();
+    }
+    prog.endStep(Phase.SAVING_CHECKPOINT, step);
+  }
+
+  /**
+   * Load cache pools from fsimage
+   */
+  private void loadPools(DataInput in)
+      throws IOException {
+    StartupProgress prog = NameNode.getStartupProgress();
+    Step step = new Step(StepType.CACHE_POOLS);
+    prog.beginStep(Phase.LOADING_FSIMAGE, step);
+    int numberOfPools = in.readInt();
+    prog.setTotal(Phase.LOADING_FSIMAGE, step, numberOfPools);
+    Counter counter = prog.getCounter(Phase.LOADING_FSIMAGE, step);
+    for (int i = 0; i < numberOfPools; i++) {
+      addCachePool(CachePoolInfo.readFrom(in));
+      counter.increment();
+    }
+    prog.endStep(Phase.LOADING_FSIMAGE, step);
+  }
+
+  /**
+   * Load cache entries from the fsimage
+   */
+  private void loadEntries(DataInput in) throws IOException {
+    StartupProgress prog = NameNode.getStartupProgress();
+    Step step = new Step(StepType.CACHE_ENTRIES);
+    prog.beginStep(Phase.LOADING_FSIMAGE, step);
+    int numberOfEntries = in.readInt();
+    prog.setTotal(Phase.LOADING_FSIMAGE, step, numberOfEntries);
+    Counter counter = prog.getCounter(Phase.LOADING_FSIMAGE, step);
+    for (int i = 0; i < numberOfEntries; i++) {
+      long entryId = in.readLong();
+      String path = Text.readString(in);
+      short replication = in.readShort();
+      String poolName = Text.readString(in);
+      // Get pool reference by looking it up in the map
+      CachePool pool = cachePools.get(poolName);
+      if (pool == null) {
+        throw new IOException("Entry refers to pool " + poolName +
+            ", which does not exist.");
+      }
+      PathBasedCacheEntry entry =
+          new PathBasedCacheEntry(entryId, path, replication, pool);
+      if (entriesById.put(entry.getEntryId(), entry) != null) {
+        throw new IOException("An entry with ID " + entry.getEntryId() +
+            " already exists");
+      }
+      List<PathBasedCacheEntry> entries = entriesByPath.get(entry.getPath());
+      if (entries == null) {
+        entries = new LinkedList<PathBasedCacheEntry>();
+        entriesByPath.put(entry.getPath(), entries);
+      }
+      entries.add(entry);
+      counter.increment();
+    }
+    prog.endStep(Phase.LOADING_FSIMAGE, step);
+  }
+}
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/CachePool.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/CachePool.java
new file mode 100644
index 0000000..0bc5bb4
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/CachePool.java
@@ -0,0 +1,197 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.server.namenode;
+
+import java.io.IOException;
+
+import javax.annotation.Nonnull;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.fs.permission.FsAction;
+import org.apache.hadoop.fs.permission.FsPermission;
+import org.apache.hadoop.hdfs.protocol.CachePoolInfo;
+import org.apache.hadoop.security.UserGroupInformation;
+
+import com.google.common.base.Preconditions;
+
+/**
+ * A CachePool describes a set of cache resources being managed by the NameNode.
+ * User caching requests are billed to the cache pool specified in the request.
+ *
+ * This is an internal class, only used on the NameNode.  For identifying or
+ * describing a cache pool to clients, please use CachePoolInfo.
+ * 
+ * CachePools must be accessed under the FSNamesystem lock.
+ */
+@InterfaceAudience.Private
+public final class CachePool {
+  public static final Log LOG = LogFactory.getLog(CachePool.class);
+
+  public static final int DEFAULT_WEIGHT = 100;
+  
+  @Nonnull
+  private final String poolName;
+
+  @Nonnull
+  private String ownerName;
+
+  @Nonnull
+  private String groupName;
+  
+  /**
+   * Cache pool permissions.
+   * 
+   * READ permission means that you can list the cache directives in this pool.
+   * WRITE permission means that you can add, remove, or modify cache directives
+   *       in this pool.
+   * EXECUTE permission is unused.
+   */
+  @Nonnull
+  private FsPermission mode;
+  
+  private int weight;
+
+  /**
+   * Create a new cache pool based on a CachePoolInfo object and the defaults.
+   * We will fill in information that was not supplied according to the
+   * defaults.
+   */
+  static CachePool createFromInfoAndDefaults(CachePoolInfo info)
+      throws IOException {
+    UserGroupInformation ugi = null;
+    String ownerName = info.getOwnerName();
+    if (ownerName == null) {
+      if (ugi == null) {
+        ugi = NameNode.getRemoteUser();
+      }
+      ownerName = ugi.getShortUserName();
+    }
+    String groupName = info.getGroupName();
+    if (groupName == null) {
+      if (ugi == null) {
+        ugi = NameNode.getRemoteUser();
+      }
+      groupName = ugi.getPrimaryGroupName();
+    }
+    FsPermission mode = (info.getMode() == null) ? 
+        FsPermission.getCachePoolDefault() : info.getMode();
+    Integer weight = (info.getWeight() == null) ?
+        DEFAULT_WEIGHT : info.getWeight();
+    return new CachePool(info.getPoolName(),
+        ownerName, groupName, mode, weight);
+  }
+
+  /**
+   * Create a new cache pool based on a CachePoolInfo object.
+   * No fields in the CachePoolInfo can be blank.
+   */
+  static CachePool createFromInfo(CachePoolInfo info) {
+    return new CachePool(info.getPoolName(),
+        info.getOwnerName(), info.getGroupName(),
+        info.getMode(), info.getWeight());
+  }
+
+  CachePool(String poolName, String ownerName, String groupName,
+      FsPermission mode, int weight) {
+    Preconditions.checkNotNull(poolName);
+    Preconditions.checkNotNull(ownerName);
+    Preconditions.checkNotNull(groupName);
+    Preconditions.checkNotNull(mode);
+    this.poolName = poolName;
+    this.ownerName = ownerName;
+    this.groupName = groupName;
+    this.mode = new FsPermission(mode);
+    this.weight = weight;
+  }
+
+  public String getPoolName() {
+    return poolName;
+  }
+
+  public String getOwnerName() {
+    return ownerName;
+  }
+
+  public CachePool setOwnerName(String ownerName) {
+    this.ownerName = ownerName;
+    return this;
+  }
+
+  public String getGroupName() {
+    return groupName;
+  }
+
+  public CachePool setGroupName(String groupName) {
+    this.groupName = groupName;
+    return this;
+  }
+
+  public FsPermission getMode() {
+    return mode;
+  }
+
+  public CachePool setMode(FsPermission mode) {
+    this.mode = new FsPermission(mode);
+    return this;
+  }
+  
+  public int getWeight() {
+    return weight;
+  }
+
+  public CachePool setWeight(int weight) {
+    this.weight = weight;
+    return this;
+  }
+  
+  /**
+   * Get information about this cache pool.
+   *
+   * @param fullInfo
+   *          If true, only the name will be returned (i.e., what you 
+   *          would get if you didn't have read permission for this pool.)
+   * @return
+   *          Cache pool information.
+   */
+  public CachePoolInfo getInfo(boolean fullInfo) {
+    CachePoolInfo info = new CachePoolInfo(poolName);
+    if (!fullInfo) {
+      return info;
+    }
+    return info.setOwnerName(ownerName).
+        setGroupName(groupName).
+        setMode(new FsPermission(mode)).
+        setWeight(weight);
+  }
+
+  public CachePoolInfo getInfo(FSPermissionChecker pc) {
+    return getInfo(pc.checkPermission(this, FsAction.READ)); 
+  }
+
+  public String toString() {
+    return new StringBuilder().
+        append("{ ").append("poolName:").append(poolName).
+        append(", ownerName:").append(ownerName).
+        append(", groupName:").append(groupName).
+        append(", mode:").append(mode).
+        append(", weight:").append(weight).
+        append(" }").toString();
+  }
+}
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/CachedBlock.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/CachedBlock.java
new file mode 100644
index 0000000..9584ea7
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/CachedBlock.java
@@ -0,0 +1,251 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.server.namenode;
+
+import java.util.Arrays;
+import java.util.LinkedList;
+import java.util.List;
+
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor;
+import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor.CachedBlocksList;
+import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor.CachedBlocksList.Type;
+import org.apache.hadoop.util.IntrusiveCollection;
+import org.apache.hadoop.util.LightWeightGSet;
+import org.apache.hadoop.util.IntrusiveCollection.Element;
+import org.apache.hadoop.util.LightWeightGSet.LinkedElement;
+
+/**
+ * Represents a cached block.
+ */
+@InterfaceAudience.LimitedPrivate({"HDFS"})
+public final class CachedBlock implements Element, 
+    LightWeightGSet.LinkedElement {
+  private static final Object[] EMPTY_ARRAY = new Object[0];
+
+  /**
+   * Block id.
+   */
+  private final long blockId;
+
+  /**
+   * Used to implement #{LightWeightGSet.LinkedElement}
+   */
+  private LinkedElement nextElement;
+
+  /**
+   * Bit 15: Mark
+   * Bit 0-14: cache replication factor.
+   */
+  private short replicationAndMark;
+
+  /**
+   * Used to implement the CachedBlocksList.
+   *
+   * Since this CachedBlock can be in multiple CachedBlocksList objects,
+   * we need to be able to store multiple 'prev' and 'next' pointers.
+   * The triplets array does this.
+   *
+   * Each triplet contains a CachedBlockList object followed by a
+   * prev pointer, followed by a next pointer.
+   */
+  private Object[] triplets;
+
+  public CachedBlock(long blockId, short replication, boolean mark) {
+    this.blockId = blockId;
+    this.triplets = EMPTY_ARRAY;
+    setReplicationAndMark(replication, mark);
+  }
+
+  public long getBlockId() {
+    return blockId;
+  }
+
+  @Override
+  public int hashCode() {
+    return (int)(blockId^(blockId>>>32));
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    if (o == null) { return false; }
+    if (o == this) { return true; }
+    if (o.getClass() != this.getClass()) {
+      return false;
+    }
+    CachedBlock other = (CachedBlock)o;
+    return other.blockId == blockId;
+  }
+
+  public void setReplicationAndMark(short replication, boolean mark) {
+    assert replication >= 0;
+    replicationAndMark = (short)((replication << 1) | (mark ? 0x1 : 0x0));
+  }
+
+  public boolean getMark() {
+    return ((replicationAndMark & 0x1) != 0);
+  }
+
+  public short getReplication() {
+    return (short) (replicationAndMark >>> 1);
+  }
+
+  /**
+   * Return true if this CachedBlock is present on the given list.
+   */
+  public boolean isPresent(CachedBlocksList cachedBlocksList) {
+    for (int i = 0; i < triplets.length; i += 3) {
+      CachedBlocksList list = (CachedBlocksList)triplets[i];
+      if (list == cachedBlocksList) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  /**
+   * Get a list of the datanodes which this block is cached,
+   * planned to be cached, or planned to be uncached on.
+   *
+   * @param type      If null, this parameter is ignored.
+   *                  If it is non-null, we match only datanodes which
+   *                  have it on this list.
+   *                  See {@link DatanodeDescriptor#CachedBlocksList#Type}
+   *                  for a description of all the lists.
+   *                  
+   * @return          The list of datanodes.  Modifying this list does not
+   *                  alter the state of the CachedBlock.
+   */
+  public List<DatanodeDescriptor> getDatanodes(Type type) {
+    List<DatanodeDescriptor> nodes = new LinkedList<DatanodeDescriptor>();
+    for (int i = 0; i < triplets.length; i += 3) {
+      CachedBlocksList list = (CachedBlocksList)triplets[i];
+      if ((type == null) || (list.getType() == type)) {
+        nodes.add(list.getDatanode());
+      }
+    }
+    return nodes;
+  }
+
+  @Override
+  public void insertInternal(IntrusiveCollection<? extends Element> list, Element prev,
+      Element next) {
+    for (int i = 0; i < triplets.length; i += 3) {
+      if (triplets[i] == list) {
+        throw new RuntimeException("Trying to re-insert an element that " +
+            "is already in the list.");
+      }
+    }
+    Object newTriplets[] = Arrays.copyOf(triplets, triplets.length + 3);
+    newTriplets[triplets.length] = list;
+    newTriplets[triplets.length + 1] = prev;
+    newTriplets[triplets.length + 2] = next;
+    triplets = newTriplets;
+  }
+  
+  @Override
+  public void setPrev(IntrusiveCollection<? extends Element> list, Element prev) {
+    for (int i = 0; i < triplets.length; i += 3) {
+      if (triplets[i] == list) {
+        triplets[i + 1] = prev;
+        return;
+      }
+    }
+    throw new RuntimeException("Called setPrev on an element that wasn't " +
+        "in the list.");
+  }
+
+  @Override
+  public void setNext(IntrusiveCollection<? extends Element> list, Element next) {
+    for (int i = 0; i < triplets.length; i += 3) {
+      if (triplets[i] == list) {
+        triplets[i + 2] = next;
+        return;
+      }
+    }
+    throw new RuntimeException("Called setNext on an element that wasn't " +
+        "in the list.");
+  }
+
+  @Override
+  public void removeInternal(IntrusiveCollection<? extends Element> list) {
+    for (int i = 0; i < triplets.length; i += 3) {
+      if (triplets[i] == list) {
+        Object[] newTriplets = new Object[triplets.length - 3];
+        System.arraycopy(triplets, 0, newTriplets, 0, i);
+        System.arraycopy(triplets, i + 3, newTriplets, i,
+            triplets.length - (i + 3));
+        triplets = newTriplets;
+        return;
+      }
+    }
+    throw new RuntimeException("Called remove on an element that wasn't " +
+        "in the list.");
+  }
+
+  @Override
+  public Element getPrev(IntrusiveCollection<? extends Element> list) {
+    for (int i = 0; i < triplets.length; i += 3) {
+      if (triplets[i] == list) {
+        return (Element)triplets[i + 1];
+      }
+    }
+    throw new RuntimeException("Called getPrev on an element that wasn't " +
+        "in the list.");
+  }
+
+  @Override
+  public Element getNext(IntrusiveCollection<? extends Element> list) {
+    for (int i = 0; i < triplets.length; i += 3) {
+      if (triplets[i] == list) {
+        return (Element)triplets[i + 2];
+      }
+    }
+    throw new RuntimeException("Called getNext on an element that wasn't " +
+        "in the list.");
+  }
+
+  @Override
+  public boolean isInList(IntrusiveCollection<? extends Element> list) {
+    for (int i = 0; i < triplets.length; i += 3) {
+      if (triplets[i] == list) {
+        return true;
+      }
+    }
+    return false;
+  }
+  
+  @Override
+  public String toString() {
+    return new StringBuilder().append("{").
+        append("blockId=").append(blockId).append(", ").
+        append("replication=").append(getReplication()).append(", ").
+        append("mark=").append(getMark()).append("}").
+        toString();
+  }
+
+  @Override // LightWeightGSet.LinkedElement 
+  public void setNext(LinkedElement next) {
+    this.nextElement = next;
+  }
+
+  @Override // LightWeightGSet.LinkedElement 
+  public LinkedElement getNext() {
+    return nextElement;
+  }
+}
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirectory.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirectory.java
index 4af1f96..5fc6ab8 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirectory.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirectory.java
@@ -53,6 +53,7 @@
 import org.apache.hadoop.hdfs.protocol.HdfsConstants;
 import org.apache.hadoop.hdfs.protocol.HdfsFileStatus;
 import org.apache.hadoop.hdfs.protocol.HdfsLocatedFileStatus;
+import org.apache.hadoop.hdfs.protocol.LocatedBlock;
 import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
 import org.apache.hadoop.hdfs.protocol.QuotaExceededException;
 import org.apache.hadoop.hdfs.protocol.SnapshotAccessControlException;
@@ -2592,12 +2593,21 @@
     int childrenNum = node.isDirectory() ? 
         node.asDirectory().getChildrenNum(snapshot) : 0;
         
-    return new HdfsLocatedFileStatus(size, node.isDirectory(), replication,
-        blocksize, node.getModificationTime(snapshot),
-        node.getAccessTime(snapshot), node.getFsPermission(snapshot),
-        node.getUserName(snapshot), node.getGroupName(snapshot),
-        node.isSymlink() ? node.asSymlink().getSymlink() : null, path,
-        node.getId(), loc, childrenNum);
+    HdfsLocatedFileStatus status =
+        new HdfsLocatedFileStatus(size, node.isDirectory(), replication,
+          blocksize, node.getModificationTime(snapshot),
+          node.getAccessTime(snapshot), node.getFsPermission(snapshot),
+          node.getUserName(snapshot), node.getGroupName(snapshot),
+          node.isSymlink() ? node.asSymlink().getSymlink() : null, path,
+          node.getId(), loc, childrenNum);
+    // Set caching information for the located blocks.
+    if (loc != null) {
+      CacheManager cacheManager = namesystem.getCacheManager();
+      for (LocatedBlock lb: loc.getLocatedBlocks()) {
+        cacheManager.setCachedLocations(lb);
+      }
+    }
+    return status;
   }
 
     
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLog.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLog.java
index 60ffe7a..10ab565 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLog.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLog.java
@@ -17,6 +17,7 @@
  */
 package org.apache.hadoop.hdfs.server.namenode;
 
+import static org.apache.hadoop.util.ExitUtil.terminate;
 import static org.apache.hadoop.util.Time.now;
 
 import java.io.IOException;
@@ -35,15 +36,18 @@
 import org.apache.hadoop.fs.Options;
 import org.apache.hadoop.fs.permission.FsPermission;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
+import org.apache.hadoop.hdfs.protocol.CachePoolInfo;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDirective;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheEntry;
 import org.apache.hadoop.hdfs.security.token.delegation.DelegationTokenIdentifier;
-
-import static org.apache.hadoop.util.ExitUtil.terminate;
-
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.NamenodeRole;
 import org.apache.hadoop.hdfs.server.common.Storage.FormatConfirmable;
 import org.apache.hadoop.hdfs.server.common.Storage.StorageDirectory;
+import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.AddCachePoolOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.AddOp;
+import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.AddPathBasedCacheDirectiveOp;
+import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.AllocateBlockIdOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.AllowSnapshotOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.CancelDelegationTokenOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.CloseOp;
@@ -55,12 +59,17 @@
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.GetDelegationTokenOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.LogSegmentOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.MkdirOp;
+import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.ModifyCachePoolOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.OpInstanceCache;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.ReassignLeaseOp;
+import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RemoveCachePoolOp;
+import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RemovePathBasedCacheDescriptorOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RenameOldOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RenameOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RenameSnapshotOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RenewDelegationTokenOp;
+import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetGenstampV1Op;
+import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetGenstampV2Op;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetOwnerOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetPermissionsOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetQuotaOp;
@@ -69,9 +78,6 @@
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.TimesOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.UpdateBlocksOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.UpdateMasterKeyOp;
-import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.AllocateBlockIdOp;
-import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetGenstampV1Op;
-import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.SetGenstampV2Op;
 import org.apache.hadoop.hdfs.server.namenode.JournalSet.JournalAndStream;
 import org.apache.hadoop.hdfs.server.namenode.metrics.NameNodeMetrics;
 import org.apache.hadoop.hdfs.server.protocol.NamenodeRegistration;
@@ -948,6 +954,45 @@
     logEdit(op);
   }
   
+  void logAddPathBasedCacheDirective(PathBasedCacheDirective directive,
+      boolean toLogRpcIds) {
+    AddPathBasedCacheDirectiveOp op = AddPathBasedCacheDirectiveOp.getInstance(
+        cache.get())
+        .setPath(directive.getPath().toUri().getPath())
+        .setReplication(directive.getReplication())
+        .setPool(directive.getPool());
+    logRpcIds(op, toLogRpcIds);
+    logEdit(op);
+  }
+
+  void logRemovePathBasedCacheDescriptor(Long id, boolean toLogRpcIds) {
+    RemovePathBasedCacheDescriptorOp op =
+        RemovePathBasedCacheDescriptorOp.getInstance(cache.get()).setId(id);
+    logRpcIds(op, toLogRpcIds);
+    logEdit(op);
+  }
+
+  void logAddCachePool(CachePoolInfo pool, boolean toLogRpcIds) {
+    AddCachePoolOp op =
+        AddCachePoolOp.getInstance(cache.get()).setPool(pool);
+    logRpcIds(op, toLogRpcIds);
+    logEdit(op);
+  }
+
+  void logModifyCachePool(CachePoolInfo info, boolean toLogRpcIds) {
+    ModifyCachePoolOp op =
+        ModifyCachePoolOp.getInstance(cache.get()).setInfo(info);
+    logRpcIds(op, toLogRpcIds);
+    logEdit(op);
+  }
+
+  void logRemoveCachePool(String poolName, boolean toLogRpcIds) {
+    RemoveCachePoolOp op =
+        RemoveCachePoolOp.getInstance(cache.get()).setPoolName(poolName);
+    logRpcIds(op, toLogRpcIds);
+    logEdit(op);
+  }
+
   /**
    * Get all the journals this edit log is currently operating on.
    */
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogLoader.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogLoader.java
index 03a1dbc..b39e19c 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogLoader.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogLoader.java
@@ -30,16 +30,21 @@
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
+import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants;
 import org.apache.hadoop.hdfs.protocol.HdfsFileStatus;
 import org.apache.hadoop.hdfs.protocol.LayoutVersion;
 import org.apache.hadoop.hdfs.protocol.LayoutVersion.Feature;
 import org.apache.hadoop.hdfs.protocol.LocatedBlock;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDescriptor;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDirective;
 import org.apache.hadoop.hdfs.server.blockmanagement.BlockInfo;
 import org.apache.hadoop.hdfs.server.blockmanagement.BlockInfoUnderConstruction;
 import org.apache.hadoop.hdfs.server.common.Storage;
+import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.AddCachePoolOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.AddCloseOp;
+import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.AddPathBasedCacheDirectiveOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.AllocateBlockIdOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.AllowSnapshotOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.BlockListUpdatingOp;
@@ -52,7 +57,10 @@
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.DisallowSnapshotOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.GetDelegationTokenOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.MkdirOp;
+import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.ModifyCachePoolOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.ReassignLeaseOp;
+import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RemoveCachePoolOp;
+import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RemovePathBasedCacheDescriptorOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RenameOldOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RenameOp;
 import org.apache.hadoop.hdfs.server.namenode.FSEditLogOp.RenameSnapshotOp;
@@ -76,6 +84,7 @@
 import org.apache.hadoop.hdfs.server.namenode.startupprogress.Step;
 import org.apache.hadoop.hdfs.util.ChunkedArrayList;
 import org.apache.hadoop.hdfs.util.Holder;
+import org.apache.jasper.tagplugins.jstl.core.Remove;
 
 import com.google.common.base.Joiner;
 
@@ -631,6 +640,54 @@
       fsNamesys.setLastAllocatedBlockId(allocateBlockIdOp.blockId);
       break;
     }
+    case OP_ADD_PATH_BASED_CACHE_DIRECTIVE: {
+      AddPathBasedCacheDirectiveOp addOp = (AddPathBasedCacheDirectiveOp) op;
+      PathBasedCacheDirective d = new PathBasedCacheDirective.Builder().
+          setPath(new Path(addOp.path)).
+          setReplication(addOp.replication).
+          setPool(addOp.pool).
+          build();
+      PathBasedCacheDescriptor descriptor =
+          fsNamesys.getCacheManager().addDirective(d, null);
+      if (toAddRetryCache) {
+        fsNamesys.addCacheEntryWithPayload(op.rpcClientId, op.rpcCallId,
+            descriptor);
+      }
+      break;
+    }
+    case OP_REMOVE_PATH_BASED_CACHE_DESCRIPTOR: {
+      RemovePathBasedCacheDescriptorOp removeOp =
+          (RemovePathBasedCacheDescriptorOp) op;
+      fsNamesys.getCacheManager().removeDescriptor(removeOp.id, null);
+      if (toAddRetryCache) {
+        fsNamesys.addCacheEntry(op.rpcClientId, op.rpcCallId);
+      }
+      break;
+    }
+    case OP_ADD_CACHE_POOL: {
+      AddCachePoolOp addOp = (AddCachePoolOp) op;
+      fsNamesys.getCacheManager().addCachePool(addOp.info);
+      if (toAddRetryCache) {
+        fsNamesys.addCacheEntry(op.rpcClientId, op.rpcCallId);
+      }
+      break;
+    }
+    case OP_MODIFY_CACHE_POOL: {
+      ModifyCachePoolOp modifyOp = (ModifyCachePoolOp) op;
+      fsNamesys.getCacheManager().modifyCachePool(modifyOp.info);
+      if (toAddRetryCache) {
+        fsNamesys.addCacheEntry(op.rpcClientId, op.rpcCallId);
+      }
+      break;
+    }
+    case OP_REMOVE_CACHE_POOL: {
+      RemoveCachePoolOp removeOp = (RemoveCachePoolOp) op;
+      fsNamesys.getCacheManager().removeCachePool(removeOp.poolName);
+      if (toAddRetryCache) {
+        fsNamesys.addCacheEntry(op.rpcClientId, op.rpcCallId);
+      }
+      break;
+    }
     default:
       throw new IOException("Invalid operation read " + op.opCode);
     }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogOp.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogOp.java
index 10432bfd..302c161 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogOp.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogOp.java
@@ -18,6 +18,8 @@
 package org.apache.hadoop.hdfs.server.namenode;
 
 import static org.apache.hadoop.hdfs.server.namenode.FSEditLogOpCodes.OP_ADD;
+import static org.apache.hadoop.hdfs.server.namenode.FSEditLogOpCodes.OP_ADD_CACHE_POOL;
+import static org.apache.hadoop.hdfs.server.namenode.FSEditLogOpCodes.OP_ADD_PATH_BASED_CACHE_DIRECTIVE;
 import static org.apache.hadoop.hdfs.server.namenode.FSEditLogOpCodes.OP_ALLOCATE_BLOCK_ID;
 import static org.apache.hadoop.hdfs.server.namenode.FSEditLogOpCodes.OP_ALLOW_SNAPSHOT;
 import static org.apache.hadoop.hdfs.server.namenode.FSEditLogOpCodes.OP_CANCEL_DELEGATION_TOKEN;
@@ -32,7 +34,10 @@
 import static org.apache.hadoop.hdfs.server.namenode.FSEditLogOpCodes.OP_GET_DELEGATION_TOKEN;
 import static org.apache.hadoop.hdfs.server.namenode.FSEditLogOpCodes.OP_INVALID;
 import static org.apache.hadoop.hdfs.server.namenode.FSEditLogOpCodes.OP_MKDIR;
+import static org.apache.hadoop.hdfs.server.namenode.FSEditLogOpCodes.OP_MODIFY_CACHE_POOL;
 import static org.apache.hadoop.hdfs.server.namenode.FSEditLogOpCodes.OP_REASSIGN_LEASE;
+import static org.apache.hadoop.hdfs.server.namenode.FSEditLogOpCodes.OP_REMOVE_CACHE_POOL;
+import static org.apache.hadoop.hdfs.server.namenode.FSEditLogOpCodes.OP_REMOVE_PATH_BASED_CACHE_DESCRIPTOR;
 import static org.apache.hadoop.hdfs.server.namenode.FSEditLogOpCodes.OP_RENAME;
 import static org.apache.hadoop.hdfs.server.namenode.FSEditLogOpCodes.OP_RENAME_OLD;
 import static org.apache.hadoop.hdfs.server.namenode.FSEditLogOpCodes.OP_RENAME_SNAPSHOT;
@@ -56,6 +61,7 @@
 import java.io.DataOutputStream;
 import java.io.EOFException;
 import java.io.IOException;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.EnumMap;
 import java.util.List;
@@ -73,6 +79,7 @@
 import org.apache.hadoop.hdfs.DFSConfigKeys;
 import org.apache.hadoop.hdfs.DeprecatedUTF8;
 import org.apache.hadoop.hdfs.protocol.Block;
+import org.apache.hadoop.hdfs.protocol.CachePoolInfo;
 import org.apache.hadoop.hdfs.protocol.ClientProtocol;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants;
 import org.apache.hadoop.hdfs.protocol.LayoutVersion;
@@ -97,7 +104,9 @@
 import org.xml.sax.SAXException;
 import org.xml.sax.helpers.AttributesImpl;
 
+import com.google.common.base.Joiner;
 import com.google.common.base.Preconditions;
+import com.google.common.base.Strings;
 
 /**
  * Helper classes for reading the ops from an InputStream.
@@ -153,6 +162,13 @@
       inst.put(OP_RENAME_SNAPSHOT, new RenameSnapshotOp());
       inst.put(OP_SET_GENSTAMP_V2, new SetGenstampV2Op());
       inst.put(OP_ALLOCATE_BLOCK_ID, new AllocateBlockIdOp());
+      inst.put(OP_ADD_PATH_BASED_CACHE_DIRECTIVE,
+          new AddPathBasedCacheDirectiveOp());
+      inst.put(OP_REMOVE_PATH_BASED_CACHE_DESCRIPTOR,
+          new RemovePathBasedCacheDescriptorOp());
+      inst.put(OP_ADD_CACHE_POOL, new AddCachePoolOp());
+      inst.put(OP_MODIFY_CACHE_POOL, new ModifyCachePoolOp());
+      inst.put(OP_REMOVE_CACHE_POOL, new RemoveCachePoolOp());
     }
     
     public FSEditLogOp get(FSEditLogOpCodes opcode) {
@@ -528,8 +544,7 @@
       } else {
         this.blocks = new Block[0];
       }
-      this.permissions =
-          permissionStatusFromXml(st.getChildren("PERMISSION_STATUS").get(0));
+      this.permissions = permissionStatusFromXml(st);
       readRpcIdsFromXml(st);
     }
   }
@@ -1208,8 +1223,7 @@
       this.inodeId = Long.valueOf(st.getValue("INODEID"));
       this.path = st.getValue("PATH");
       this.timestamp = Long.valueOf(st.getValue("TIMESTAMP"));
-      this.permissions =
-          permissionStatusFromXml(st.getChildren("PERMISSION_STATUS").get(0));
+      this.permissions = permissionStatusFromXml(st);
     }
   }
 
@@ -1940,8 +1954,7 @@
       this.value = st.getValue("VALUE");
       this.mtime = Long.valueOf(st.getValue("MTIME"));
       this.atime = Long.valueOf(st.getValue("ATIME"));
-      this.permissionStatus =
-          permissionStatusFromXml(st.getChildren("PERMISSION_STATUS").get(0));
+      this.permissionStatus = permissionStatusFromXml(st);
       
       readRpcIdsFromXml(st);
     }
@@ -2848,6 +2861,317 @@
     }
   }
 
+  /**
+   * {@literal @AtMostOnce} for
+   * {@link ClientProtocol#addPathBasedCacheDirective}
+   */
+  static class AddPathBasedCacheDirectiveOp extends FSEditLogOp {
+    String path;
+    short replication;
+    String pool;
+
+    public AddPathBasedCacheDirectiveOp() {
+      super(OP_ADD_PATH_BASED_CACHE_DIRECTIVE);
+    }
+
+    static AddPathBasedCacheDirectiveOp getInstance(OpInstanceCache cache) {
+      return (AddPathBasedCacheDirectiveOp) cache
+          .get(OP_ADD_PATH_BASED_CACHE_DIRECTIVE);
+    }
+
+    public AddPathBasedCacheDirectiveOp setPath(String path) {
+      this.path = path;
+      return this;
+    }
+
+    public AddPathBasedCacheDirectiveOp setReplication(short replication) {
+      this.replication = replication;
+      return this;
+    }
+
+    public AddPathBasedCacheDirectiveOp setPool(String pool) {
+      this.pool = pool;
+      return this;
+    }
+
+    @Override
+    void readFields(DataInputStream in, int logVersion) throws IOException {
+      this.path = FSImageSerialization.readString(in);
+      this.replication = FSImageSerialization.readShort(in);
+      this.pool = FSImageSerialization.readString(in);
+      readRpcIds(in, logVersion);
+    }
+
+    @Override
+    public void writeFields(DataOutputStream out) throws IOException {
+      FSImageSerialization.writeString(path, out);
+      FSImageSerialization.writeShort(replication, out);
+      FSImageSerialization.writeString(pool, out);
+      writeRpcIds(rpcClientId, rpcCallId, out);
+    }
+
+    @Override
+    protected void toXml(ContentHandler contentHandler) throws SAXException {
+      XMLUtils.addSaxString(contentHandler, "PATH", path);
+      XMLUtils.addSaxString(contentHandler, "REPLICATION",
+          Short.toString(replication));
+      XMLUtils.addSaxString(contentHandler, "POOL", pool);
+      appendRpcIdsToXml(contentHandler, rpcClientId, rpcCallId);
+    }
+
+    @Override
+    void fromXml(Stanza st) throws InvalidXmlException {
+      path = st.getValue("PATH");
+      replication = Short.parseShort(st.getValue("REPLICATION"));
+      pool = st.getValue("POOL");
+      readRpcIdsFromXml(st);
+    }
+
+    @Override
+    public String toString() {
+      StringBuilder builder = new StringBuilder();
+      builder.append("AddPathBasedCacheDirective [");
+      builder.append("path=" + path + ",");
+      builder.append("replication=" + replication + ",");
+      builder.append("pool=" + pool);
+      appendRpcIdsToString(builder, rpcClientId, rpcCallId);
+      builder.append("]");
+      return builder.toString();
+    }
+  }
+
+  /**
+   * {@literal @AtMostOnce} for
+   * {@link ClientProtocol#removePathBasedCacheDescriptor}
+   */
+  static class RemovePathBasedCacheDescriptorOp extends FSEditLogOp {
+    long id;
+
+    public RemovePathBasedCacheDescriptorOp() {
+      super(OP_REMOVE_PATH_BASED_CACHE_DESCRIPTOR);
+    }
+
+    static RemovePathBasedCacheDescriptorOp getInstance(OpInstanceCache cache) {
+      return (RemovePathBasedCacheDescriptorOp) cache
+          .get(OP_REMOVE_PATH_BASED_CACHE_DESCRIPTOR);
+    }
+
+    public RemovePathBasedCacheDescriptorOp setId(long id) {
+      this.id = id;
+      return this;
+    }
+
+    @Override
+    void readFields(DataInputStream in, int logVersion) throws IOException {
+      this.id = FSImageSerialization.readLong(in);
+      readRpcIds(in, logVersion);
+    }
+
+    @Override
+    public void writeFields(DataOutputStream out) throws IOException {
+      FSImageSerialization.writeLong(id, out);
+      writeRpcIds(rpcClientId, rpcCallId, out);
+    }
+
+    @Override
+    protected void toXml(ContentHandler contentHandler) throws SAXException {
+      XMLUtils.addSaxString(contentHandler, "ID", Long.toString(id));
+      appendRpcIdsToXml(contentHandler, rpcClientId, rpcCallId);
+    }
+
+    @Override
+    void fromXml(Stanza st) throws InvalidXmlException {
+      this.id = Long.parseLong(st.getValue("ID"));
+      readRpcIdsFromXml(st);
+    }
+
+    @Override
+    public String toString() {
+      StringBuilder builder = new StringBuilder();
+      builder.append("RemovePathBasedCacheDescriptor [");
+      builder.append("id=" + Long.toString(id));
+      appendRpcIdsToString(builder, rpcClientId, rpcCallId);
+      builder.append("]");
+      return builder.toString();
+    }
+  }
+
+  /** {@literal @AtMostOnce} for {@link ClientProtocol#addCachePool} */
+  static class AddCachePoolOp extends FSEditLogOp {
+    CachePoolInfo info;
+
+    public AddCachePoolOp() {
+      super(OP_ADD_CACHE_POOL);
+    }
+
+    static AddCachePoolOp getInstance(OpInstanceCache cache) {
+      return (AddCachePoolOp) cache.get(OP_ADD_CACHE_POOL);
+    }
+
+    public AddCachePoolOp setPool(CachePoolInfo info) {
+      this.info = info;
+      return this;
+    }
+
+    @Override
+    void readFields(DataInputStream in, int logVersion) throws IOException {
+      info = CachePoolInfo.readFrom(in);
+      readRpcIds(in, logVersion);
+    }
+
+    @Override
+    public void writeFields(DataOutputStream out) throws IOException {
+      info .writeTo(out);
+      writeRpcIds(rpcClientId, rpcCallId, out);
+    }
+
+    @Override
+    protected void toXml(ContentHandler contentHandler) throws SAXException {
+      info.writeXmlTo(contentHandler);
+      appendRpcIdsToXml(contentHandler, rpcClientId, rpcCallId);
+    }
+
+    @Override
+    void fromXml(Stanza st) throws InvalidXmlException {
+      this.info = CachePoolInfo.readXmlFrom(st);
+      readRpcIdsFromXml(st);
+    }
+
+    @Override
+    public String toString() {
+      StringBuilder builder = new StringBuilder();
+      builder.append("AddCachePoolOp [");
+      builder.append("poolName=" + info.getPoolName() + ",");
+      builder.append("ownerName=" + info.getOwnerName() + ",");
+      builder.append("groupName=" + info.getGroupName() + ",");
+      builder.append("mode=" + Short.toString(info.getMode().toShort()) + ",");
+      builder.append("weight=" + Integer.toString(info.getWeight()));
+      appendRpcIdsToString(builder, rpcClientId, rpcCallId);
+      builder.append("]");
+      return builder.toString();
+    }
+  }
+
+  /** {@literal @AtMostOnce} for {@link ClientProtocol#modifyCachePool} */
+  static class ModifyCachePoolOp extends FSEditLogOp {
+    CachePoolInfo info;
+
+    public ModifyCachePoolOp() {
+      super(OP_MODIFY_CACHE_POOL);
+    }
+
+    static ModifyCachePoolOp getInstance(OpInstanceCache cache) {
+      return (ModifyCachePoolOp) cache.get(OP_MODIFY_CACHE_POOL);
+    }
+
+    public ModifyCachePoolOp setInfo(CachePoolInfo info) {
+      this.info = info;
+      return this;
+    }
+
+    @Override
+    void readFields(DataInputStream in, int logVersion) throws IOException {
+      info = CachePoolInfo.readFrom(in);
+      readRpcIds(in, logVersion);
+    }
+
+    @Override
+    public void writeFields(DataOutputStream out) throws IOException {
+      info.writeTo(out);
+      writeRpcIds(rpcClientId, rpcCallId, out);
+    }
+
+    @Override
+    protected void toXml(ContentHandler contentHandler) throws SAXException {
+      cachePoolInfoToXml(contentHandler, info);
+      appendRpcIdsToXml(contentHandler, rpcClientId, rpcCallId);
+    }
+
+    @Override
+    void fromXml(Stanza st) throws InvalidXmlException {
+      this.info = cachePoolInfoFromXml(st);
+      readRpcIdsFromXml(st);
+    }
+
+    @Override
+    public String toString() {
+      StringBuilder builder = new StringBuilder();
+      builder.append("ModifyCachePoolOp [");
+      ArrayList<String> fields = new ArrayList<String>(5);
+      if (info.getPoolName() != null) {
+        fields.add("poolName=" + info.getPoolName());
+      }
+      if (info.getOwnerName() != null) {
+        fields.add("ownerName=" + info.getOwnerName());
+      }
+      if (info.getGroupName() != null) {
+        fields.add("groupName=" + info.getGroupName());
+      }
+      if (info.getMode() != null) {
+        fields.add("mode=" + info.getMode().toString());
+      }
+      if (info.getWeight() != null) {
+        fields.add("weight=" + info.getWeight());
+      }
+      builder.append(Joiner.on(",").join(fields));
+      appendRpcIdsToString(builder, rpcClientId, rpcCallId);
+      builder.append("]");
+      return builder.toString();
+    }
+  }
+
+  /** {@literal @AtMostOnce} for {@link ClientProtocol#removeCachePool} */
+  static class RemoveCachePoolOp extends FSEditLogOp {
+    String poolName;
+
+    public RemoveCachePoolOp() {
+      super(OP_REMOVE_CACHE_POOL);
+    }
+
+    static RemoveCachePoolOp getInstance(OpInstanceCache cache) {
+      return (RemoveCachePoolOp) cache.get(OP_REMOVE_CACHE_POOL);
+    }
+
+    public RemoveCachePoolOp setPoolName(String poolName) {
+      this.poolName = poolName;
+      return this;
+    }
+
+    @Override
+    void readFields(DataInputStream in, int logVersion) throws IOException {
+      poolName = FSImageSerialization.readString(in);
+      readRpcIds(in, logVersion);
+    }
+
+    @Override
+    public void writeFields(DataOutputStream out) throws IOException {
+      FSImageSerialization.writeString(poolName, out);
+      writeRpcIds(rpcClientId, rpcCallId, out);
+    }
+
+    @Override
+    protected void toXml(ContentHandler contentHandler) throws SAXException {
+      XMLUtils.addSaxString(contentHandler, "POOLNAME", poolName);
+      appendRpcIdsToXml(contentHandler, rpcClientId, rpcCallId);
+    }
+
+    @Override
+    void fromXml(Stanza st) throws InvalidXmlException {
+      this.poolName = st.getValue("POOLNAME");
+      readRpcIdsFromXml(st);
+    }
+
+    @Override
+    public String toString() {
+      StringBuilder builder = new StringBuilder();
+      builder.append("RemoveCachePoolOp [");
+      builder.append("poolName=" + poolName);
+      appendRpcIdsToString(builder, rpcClientId, rpcCallId);
+      builder.append("]");
+      return builder.toString();
+    }
+  }
+
   static private short readShort(DataInputStream in) throws IOException {
     return Short.parseShort(FSImageSerialization.readString(in));
   }
@@ -3235,16 +3559,65 @@
     contentHandler.startElement("", "", "PERMISSION_STATUS", new AttributesImpl());
     XMLUtils.addSaxString(contentHandler, "USERNAME", perm.getUserName());
     XMLUtils.addSaxString(contentHandler, "GROUPNAME", perm.getGroupName());
-    XMLUtils.addSaxString(contentHandler, "MODE",
-        Short.valueOf(perm.getPermission().toShort()).toString());
+    fsPermissionToXml(contentHandler, perm.getPermission());
     contentHandler.endElement("", "", "PERMISSION_STATUS");
   }
 
   public static PermissionStatus permissionStatusFromXml(Stanza st)
       throws InvalidXmlException {
-    String username = st.getValue("USERNAME");
-    String groupname = st.getValue("GROUPNAME");
+    Stanza status = st.getChildren("PERMISSION_STATUS").get(0);
+    String username = status.getValue("USERNAME");
+    String groupname = status.getValue("GROUPNAME");
+    FsPermission mode = fsPermissionFromXml(status);
+    return new PermissionStatus(username, groupname, mode);
+  }
+
+  public static void fsPermissionToXml(ContentHandler contentHandler,
+      FsPermission mode) throws SAXException {
+    XMLUtils.addSaxString(contentHandler, "MODE", Short.valueOf(mode.toShort())
+        .toString());
+  }
+
+  public static FsPermission fsPermissionFromXml(Stanza st)
+      throws InvalidXmlException {
     short mode = Short.valueOf(st.getValue("MODE"));
-    return new PermissionStatus(username, groupname, new FsPermission(mode));
+    return new FsPermission(mode);
+  }
+
+  public static void cachePoolInfoToXml(ContentHandler contentHandler,
+      CachePoolInfo info) throws SAXException {
+    XMLUtils.addSaxString(contentHandler, "POOLNAME", info.getPoolName());
+    if (info.getOwnerName() != null) {
+      XMLUtils.addSaxString(contentHandler, "OWNERNAME", info.getOwnerName());
+    }
+    if (info.getGroupName() != null) {
+      XMLUtils.addSaxString(contentHandler, "GROUPNAME", info.getGroupName());
+    }
+    if (info.getMode() != null) {
+      fsPermissionToXml(contentHandler, info.getMode());
+    }
+    if (info.getWeight() != null) {
+      XMLUtils.addSaxString(contentHandler, "WEIGHT",
+          Integer.toString(info.getWeight()));
+    }
+  }
+
+  public static CachePoolInfo cachePoolInfoFromXml(Stanza st)
+      throws InvalidXmlException {
+    String poolName = st.getValue("POOLNAME");
+    CachePoolInfo info = new CachePoolInfo(poolName);
+    if (st.hasChildren("OWNERNAME")) {
+      info.setOwnerName(st.getValue("OWNERNAME"));
+    }
+    if (st.hasChildren("GROUPNAME")) {
+      info.setGroupName(st.getValue("GROUPNAME"));
+    }
+    if (st.hasChildren("MODE")) {
+      info.setMode(FSEditLogOp.fsPermissionFromXml(st));
+    }
+    if (st.hasChildren("WEIGHT")) {
+      info.setWeight(Integer.parseInt(st.getValue("WEIGHT")));
+    }
+    return info;
   }
 }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogOpCodes.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogOpCodes.java
index 751eb10..b9efc1e 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogOpCodes.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogOpCodes.java
@@ -63,7 +63,13 @@
   OP_ALLOW_SNAPSHOT             ((byte) 29),
   OP_DISALLOW_SNAPSHOT          ((byte) 30),
   OP_SET_GENSTAMP_V2            ((byte) 31),
-  OP_ALLOCATE_BLOCK_ID          ((byte) 32);
+  OP_ALLOCATE_BLOCK_ID          ((byte) 32),
+  OP_ADD_PATH_BASED_CACHE_DIRECTIVE        ((byte) 33),
+  OP_REMOVE_PATH_BASED_CACHE_DESCRIPTOR    ((byte) 34),
+  OP_ADD_CACHE_POOL             ((byte) 35),
+  OP_MODIFY_CACHE_POOL          ((byte) 36),
+  OP_REMOVE_CACHE_POOL          ((byte) 37);
+
   private byte opCode;
 
   /**
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImageFormat.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImageFormat.java
index 74f5219..34659fb 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImageFormat.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSImageFormat.java
@@ -351,6 +351,8 @@
 
         loadSecretManagerState(in);
 
+        loadCacheManagerState(in);
+
         // make sure to read to the end of file
         boolean eof = (in.read() == -1);
         assert eof : "Should have reached the end of image file " + curFile;
@@ -843,6 +845,14 @@
       namesystem.loadSecretManagerState(in);
     }
 
+    private void loadCacheManagerState(DataInput in) throws IOException {
+      int imgVersion = getLayoutVersion();
+      if (!LayoutVersion.supports(Feature.CACHING, imgVersion)) {
+        return;
+      }
+      namesystem.getCacheManager().loadState(in);
+    }
+
     private int getLayoutVersion() {
       return namesystem.getFSImage().getStorage().getLayoutVersion();
     }
@@ -985,6 +995,8 @@
         context.checkCancelled();
         sourceNamesystem.saveSecretManagerState(out, sdPath);
         context.checkCancelled();
+        sourceNamesystem.getCacheManager().saveState(out, sdPath);
+        context.checkCancelled();
         out.flush();
         context.checkCancelled();
         fout.getChannel().force(true);
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java
index 8f1ef3c..7f58a20 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java
@@ -121,6 +121,7 @@
 import org.apache.hadoop.HadoopIllegalArgumentException;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.BatchedRemoteIterator.BatchedListEntries;
 import org.apache.hadoop.fs.ContentSummary;
 import org.apache.hadoop.fs.CreateFlag;
 import org.apache.hadoop.fs.DirectoryListingStartAfterNotFoundException;
@@ -144,6 +145,8 @@
 import org.apache.hadoop.hdfs.HdfsConfiguration;
 import org.apache.hadoop.hdfs.protocol.AlreadyBeingCreatedException;
 import org.apache.hadoop.hdfs.protocol.Block;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDirective;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDescriptor;
 import org.apache.hadoop.hdfs.protocol.ClientProtocol;
 import org.apache.hadoop.hdfs.protocol.DatanodeID;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
@@ -155,6 +158,7 @@
 import org.apache.hadoop.hdfs.protocol.HdfsFileStatus;
 import org.apache.hadoop.hdfs.protocol.LocatedBlock;
 import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
+import org.apache.hadoop.hdfs.protocol.CachePoolInfo;
 import org.apache.hadoop.hdfs.protocol.QuotaExceededException;
 import org.apache.hadoop.hdfs.protocol.RecoveryInProgressException;
 import org.apache.hadoop.hdfs.protocol.SnapshotDiffReport;
@@ -379,6 +383,7 @@
   FSDirectory dir;
   private final BlockManager blockManager;
   private final SnapshotManager snapshotManager;
+  private final CacheManager cacheManager;
   private final DatanodeStatistics datanodeStatistics;
 
   // Block pool ID used by this namenode
@@ -714,6 +719,12 @@
       this.dtSecretManager = createDelegationTokenSecretManager(conf);
       this.dir = new FSDirectory(fsImage, this, conf);
       this.snapshotManager = new SnapshotManager(dir);
+      writeLock();
+      try {
+        this.cacheManager = new CacheManager(this, conf, blockManager);
+      } finally {
+        writeUnlock();
+      }
       this.safeMode = new SafeModeInfo(conf);
       this.auditLoggers = initAuditLoggers(conf);
       this.isDefaultAuditLogger = auditLoggers.size() == 1 &&
@@ -906,6 +917,7 @@
     writeLock();
     try {
       if (blockManager != null) blockManager.close();
+      cacheManager.deactivate();
     } finally {
       writeUnlock();
     }
@@ -937,7 +949,7 @@
         blockManager.getDatanodeManager().markAllDatanodesStale();
         blockManager.clearQueues();
         blockManager.processAllPendingDNMessages();
-        
+
         if (!isInSafeMode() ||
             (isInSafeMode() && safeMode.isPopulatingReplQueues())) {
           LOG.info("Reprocessing replication and invalidation queues");
@@ -970,6 +982,8 @@
       //ResourceMonitor required only at ActiveNN. See HDFS-2914
       this.nnrmthread = new Daemon(new NameNodeResourceMonitor());
       nnrmthread.start();
+      cacheManager.activate();
+      blockManager.getDatanodeManager().setSendCachingCommands(true);
     } finally {
       writeUnlock();
       startingActiveService = false;
@@ -1015,6 +1029,8 @@
         // so that the tailer starts from the right spot.
         dir.fsImage.updateLastAppliedTxIdFromWritten();
       }
+      cacheManager.deactivate();
+      blockManager.getDatanodeManager().setSendCachingCommands(false);
     } finally {
       writeUnlock();
     }
@@ -1588,8 +1604,14 @@
           length = Math.min(length, fileSize - offset);
           isUc = false;
         }
-        return blockManager.createLocatedBlocks(inode.getBlocks(), fileSize,
+        LocatedBlocks blocks =
+          blockManager.createLocatedBlocks(inode.getBlocks(), fileSize,
             isUc, offset, length, needBlockToken, iip.isSnapshot());
+        // Set caching information for the located blocks.
+        for (LocatedBlock lb: blocks.getLocatedBlocks()) {
+          cacheManager.setCachedLocations(lb);
+        }
+        return blocks;
       } finally {
         if (isReadOp) {
           readUnlock();
@@ -4053,15 +4075,15 @@
    */
   HeartbeatResponse handleHeartbeat(DatanodeRegistration nodeReg,
       long capacity, long dfsUsed, long remaining, long blockPoolUsed,
-      int xceiverCount, int xmitsInProgress, int failedVolumes) 
-        throws IOException {
+      long cacheCapacity, long cacheUsed, int xceiverCount, int xmitsInProgress,
+      int failedVolumes) throws IOException {
     readLock();
     try {
       final int maxTransfer = blockManager.getMaxReplicationStreams()
           - xmitsInProgress;
       DatanodeCommand[] cmds = blockManager.getDatanodeManager().handleHeartbeat(
           nodeReg, blockPoolId, capacity, dfsUsed, remaining, blockPoolUsed,
-          xceiverCount, maxTransfer, failedVolumes);
+          cacheCapacity, cacheUsed, xceiverCount, maxTransfer, failedVolumes);
       return new HeartbeatResponse(cmds, createHaStatusHeartbeat());
     } finally {
       readUnlock();
@@ -6518,6 +6540,10 @@
   public FSDirectory getFSDirectory() {
     return dir;
   }
+  /** @return the cache manager. */
+  public CacheManager getCacheManager() {
+    return cacheManager;
+  }
 
   @Override  // NameNodeMXBean
   public String getCorruptFiles() {
@@ -6894,6 +6920,215 @@
     }
   }
 
+  PathBasedCacheDescriptor addPathBasedCacheDirective(
+      PathBasedCacheDirective directive) throws IOException {
+    checkOperation(OperationCategory.WRITE);
+    final FSPermissionChecker pc = isPermissionEnabled ?
+        getPermissionChecker() : null;
+    CacheEntryWithPayload cacheEntry =
+        RetryCache.waitForCompletion(retryCache, null);
+    if (cacheEntry != null && cacheEntry.isSuccess()) {
+      return (PathBasedCacheDescriptor) cacheEntry.getPayload();
+    }
+    boolean success = false;
+    PathBasedCacheDescriptor result = null;
+    writeLock();
+    try {
+      checkOperation(OperationCategory.WRITE);
+      if (isInSafeMode()) {
+        throw new SafeModeException(
+            "Cannot add PathBasedCache directive", safeMode);
+      }
+      result = cacheManager.addDirective(directive, pc);
+      getEditLog().logAddPathBasedCacheDirective(directive,
+          cacheEntry != null);
+      success = true;
+    } finally {
+      writeUnlock();
+      if (success) {
+        getEditLog().logSync();
+      }
+      if (isAuditEnabled() && isExternalInvocation()) {
+        logAuditEvent(success, "addPathBasedCacheDirective", null, null, null);
+      }
+      RetryCache.setState(cacheEntry, success, result);
+    }
+    return result;
+  }
+
+  void removePathBasedCacheDescriptor(Long id) throws IOException {
+    checkOperation(OperationCategory.WRITE);
+    final FSPermissionChecker pc = isPermissionEnabled ?
+        getPermissionChecker() : null;
+    CacheEntry cacheEntry = RetryCache.waitForCompletion(retryCache);
+    if (cacheEntry != null && cacheEntry.isSuccess()) {
+      return;
+    }
+    boolean success = false;
+    writeLock();
+    try {
+      checkOperation(OperationCategory.WRITE);
+      if (isInSafeMode()) {
+        throw new SafeModeException(
+            "Cannot remove PathBasedCache directives", safeMode);
+      }
+      cacheManager.removeDescriptor(id, pc);
+      getEditLog().logRemovePathBasedCacheDescriptor(id, cacheEntry != null);
+      success = true;
+    } finally {
+      writeUnlock();
+      if (isAuditEnabled() && isExternalInvocation()) {
+        logAuditEvent(success, "removePathBasedCacheDescriptor", null, null,
+            null);
+      }
+      RetryCache.setState(cacheEntry, success);
+    }
+    getEditLog().logSync();
+  }
+
+  BatchedListEntries<PathBasedCacheDescriptor> listPathBasedCacheDescriptors(
+      long startId, String pool, String path) throws IOException {
+    checkOperation(OperationCategory.READ);
+    final FSPermissionChecker pc = isPermissionEnabled ?
+        getPermissionChecker() : null;
+    BatchedListEntries<PathBasedCacheDescriptor> results;
+    readLock();
+    boolean success = false;
+    try {
+      checkOperation(OperationCategory.READ);
+      results =
+          cacheManager.listPathBasedCacheDescriptors(startId, pool, path, pc);
+      success = true;
+    } finally {
+      readUnlock();
+      if (isAuditEnabled() && isExternalInvocation()) {
+        logAuditEvent(success, "listPathBasedCacheDescriptors", null, null,
+            null);
+      }
+    }
+    return results;
+  }
+
+  public void addCachePool(CachePoolInfo req) throws IOException {
+    checkOperation(OperationCategory.WRITE);
+    final FSPermissionChecker pc = isPermissionEnabled ?
+        getPermissionChecker() : null;
+    CacheEntry cacheEntry = RetryCache.waitForCompletion(retryCache);
+    if (cacheEntry != null && cacheEntry.isSuccess()) {
+      return; // Return previous response
+    }
+    writeLock();
+    boolean success = false;
+    try {
+      checkOperation(OperationCategory.WRITE);
+      if (isInSafeMode()) {
+        throw new SafeModeException(
+            "Cannot add cache pool " + req.getPoolName(), safeMode);
+      }
+      if (pc != null) {
+        pc.checkSuperuserPrivilege();
+      }
+      CachePoolInfo info = cacheManager.addCachePool(req);
+      getEditLog().logAddCachePool(info, cacheEntry != null);
+      success = true;
+    } finally {
+      writeUnlock();
+      if (isAuditEnabled() && isExternalInvocation()) {
+        logAuditEvent(success, "addCachePool", req.getPoolName(), null, null);
+      }
+      RetryCache.setState(cacheEntry, success);
+    }
+    
+    getEditLog().logSync();
+  }
+
+  public void modifyCachePool(CachePoolInfo req) throws IOException {
+    checkOperation(OperationCategory.WRITE);
+    final FSPermissionChecker pc =
+        isPermissionEnabled ? getPermissionChecker() : null;
+    CacheEntry cacheEntry = RetryCache.waitForCompletion(retryCache);
+    if (cacheEntry != null && cacheEntry.isSuccess()) {
+      return; // Return previous response
+    }
+    writeLock();
+    boolean success = false;
+    try {
+      checkOperation(OperationCategory.WRITE);
+      if (isInSafeMode()) {
+        throw new SafeModeException(
+            "Cannot modify cache pool " + req.getPoolName(), safeMode);
+      }
+      if (pc != null) {
+        pc.checkSuperuserPrivilege();
+      }
+      cacheManager.modifyCachePool(req);
+      getEditLog().logModifyCachePool(req, cacheEntry != null);
+      success = true;
+    } finally {
+      writeUnlock();
+      if (isAuditEnabled() && isExternalInvocation()) {
+        logAuditEvent(success, "modifyCachePool", req.getPoolName(), null, null);
+      }
+      RetryCache.setState(cacheEntry, success);
+    }
+
+    getEditLog().logSync();
+  }
+
+  public void removeCachePool(String cachePoolName) throws IOException {
+    checkOperation(OperationCategory.WRITE);
+    final FSPermissionChecker pc =
+        isPermissionEnabled ? getPermissionChecker() : null;
+    CacheEntry cacheEntry = RetryCache.waitForCompletion(retryCache);
+    if (cacheEntry != null && cacheEntry.isSuccess()) {
+      return; // Return previous response
+    }
+    writeLock();
+    boolean success = false;
+    try {
+      checkOperation(OperationCategory.WRITE);
+      if (isInSafeMode()) {
+        throw new SafeModeException(
+            "Cannot remove cache pool " + cachePoolName, safeMode);
+      }
+      if (pc != null) {
+        pc.checkSuperuserPrivilege();
+      }
+      cacheManager.removeCachePool(cachePoolName);
+      getEditLog().logRemoveCachePool(cachePoolName, cacheEntry != null);
+      success = true;
+    } finally {
+      writeUnlock();
+      if (isAuditEnabled() && isExternalInvocation()) {
+        logAuditEvent(success, "removeCachePool", cachePoolName, null, null);
+      }
+      RetryCache.setState(cacheEntry, success);
+    }
+    
+    getEditLog().logSync();
+  }
+
+  public BatchedListEntries<CachePoolInfo> listCachePools(String prevKey)
+      throws IOException {
+    final FSPermissionChecker pc =
+        isPermissionEnabled ? getPermissionChecker() : null;
+    BatchedListEntries<CachePoolInfo> results;
+    checkOperation(OperationCategory.READ);
+    boolean success = false;
+    readLock();
+    try {
+      checkOperation(OperationCategory.READ);
+      results = cacheManager.listCachePools(pc, prevKey);
+      success = true;
+    } finally {
+      readUnlock();
+      if (isAuditEnabled() && isExternalInvocation()) {
+        logAuditEvent(success, "listCachePools", null, null, null);
+      }
+    }
+    return results;
+  }
+
   /**
    * Default AuditLogger implementation; used when no access logger is
    * defined in the config file. It can also be explicitly listed in the
@@ -6951,10 +7186,8 @@
         logAuditMessage(sb.toString());
       }
     }
-
     public void logAuditMessage(String message) {
       auditLog.info(message);
     }
   }
-
 }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSPermissionChecker.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSPermissionChecker.java
index a02bc40..644a639 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSPermissionChecker.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSPermissionChecker.java
@@ -255,4 +255,30 @@
     throw new AccessControlException("Permission denied by sticky bit setting:" +
       " user=" + user + ", inode=" + inode);
   }
+
+  /**
+   * Whether a cache pool can be accessed by the current context
+   *
+   * @param pool CachePool being accessed
+   * @param access type of action being performed on the cache pool
+   * @return if the pool can be accessed
+   */
+  public boolean checkPermission(CachePool pool, FsAction access) {
+    FsPermission mode = pool.getMode();
+    if (isSuperUser()) {
+      return true;
+    }
+    if (user.equals(pool.getOwnerName())
+        && mode.getUserAction().implies(access)) {
+      return true;
+    }
+    if (groups.contains(pool.getGroupName())
+        && mode.getGroupAction().implies(access)) {
+      return true;
+    }
+    if (mode.getOtherAction().implies(access)) {
+      return true;
+    }
+    return false;
+  }
 }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNode.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNode.java
index ca31d5f9..347a92e 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNode.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNode.java
@@ -686,8 +686,13 @@
     try {
       initializeGenericKeys(conf, nsId, namenodeId);
       initialize(conf);
-      state.prepareToEnterState(haContext);
-      state.enterState(haContext);
+      try {
+        haContext.writeLock();
+        state.prepareToEnterState(haContext);
+        state.enterState(haContext);
+      } finally {
+        haContext.writeUnlock();
+      }
     } catch (IOException e) {
       this.stop();
       throw e;
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNodeRpcServer.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNodeRpcServer.java
index 6980578..162a915 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNodeRpcServer.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNodeRpcServer.java
@@ -36,6 +36,7 @@
 import org.apache.commons.logging.Log;
 import org.apache.hadoop.HadoopIllegalArgumentException;
 import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.BatchedRemoteIterator;
 import org.apache.hadoop.fs.CommonConfigurationKeys;
 import org.apache.hadoop.fs.ContentSummary;
 import org.apache.hadoop.fs.CreateFlag;
@@ -45,6 +46,7 @@
 import org.apache.hadoop.fs.Options;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.fs.ParentNotDirectoryException;
+import org.apache.hadoop.fs.RemoteIterator;
 import org.apache.hadoop.fs.UnresolvedLinkException;
 import org.apache.hadoop.fs.permission.FsPermission;
 import org.apache.hadoop.fs.permission.PermissionStatus;
@@ -59,6 +61,9 @@
 import org.apache.hadoop.hdfs.HDFSPolicyProvider;
 import org.apache.hadoop.hdfs.protocol.AlreadyBeingCreatedException;
 import org.apache.hadoop.hdfs.protocol.BlockListAsLongs;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDirective;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDescriptor;
+import org.apache.hadoop.hdfs.protocol.CachePoolInfo;
 import org.apache.hadoop.hdfs.protocol.CorruptFileBlocks;
 import org.apache.hadoop.hdfs.protocol.DatanodeID;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
@@ -956,13 +961,14 @@
 
   @Override // DatanodeProtocol
   public HeartbeatResponse sendHeartbeat(DatanodeRegistration nodeReg,
-      StorageReport[] report, int xmitsInProgress, int xceiverCount,
+      StorageReport[] report, long dnCacheCapacity, long dnCacheUsed,
+      int xmitsInProgress, int xceiverCount,
       int failedVolumes) throws IOException {
     verifyRequest(nodeReg);
     return namesystem.handleHeartbeat(nodeReg, report[0].getCapacity(),
         report[0].getDfsUsed(), report[0].getRemaining(),
-        report[0].getBlockPoolUsed(), xceiverCount, xmitsInProgress,
-        failedVolumes);
+        report[0].getBlockPoolUsed(), dnCacheCapacity, dnCacheUsed,
+        xceiverCount, xmitsInProgress, failedVolumes);
   }
 
   @Override // DatanodeProtocol
@@ -982,6 +988,18 @@
     return null;
   }
 
+  @Override
+  public DatanodeCommand cacheReport(DatanodeRegistration nodeReg,
+      String poolId, List<Long> blockIds) throws IOException {
+    verifyRequest(nodeReg);
+    if (blockStateChangeLog.isDebugEnabled()) {
+      blockStateChangeLog.debug("*BLOCK* NameNode.cacheReport: "
+           + "from " + nodeReg + " " + blockIds.size() + " blocks");
+    }
+    namesystem.getCacheManager().processCacheReport(nodeReg, blockIds);
+    return null;
+  }
+
   @Override // DatanodeProtocol
   public void blockReceivedAndDeleted(DatanodeRegistration nodeReg, String poolId,
       StorageReceivedDeletedBlocks[] receivedAndDeletedBlocks) throws IOException {
@@ -1214,4 +1232,87 @@
     metrics.incrSnapshotDiffReportOps();
     return report;
   }
+
+  @Override
+  public PathBasedCacheDescriptor addPathBasedCacheDirective(
+      PathBasedCacheDirective path) throws IOException {
+    return namesystem.addPathBasedCacheDirective(path);
+  }
+
+  @Override
+  public void removePathBasedCacheDescriptor(Long id) throws IOException {
+    namesystem.removePathBasedCacheDescriptor(id);
+  }
+
+  private class ServerSidePathBasedCacheEntriesIterator
+      extends BatchedRemoteIterator<Long, PathBasedCacheDescriptor> {
+
+    private final String pool;
+
+    private final String path;
+
+    public ServerSidePathBasedCacheEntriesIterator(Long firstKey, String pool,
+        String path) {
+      super(firstKey);
+      this.pool = pool;
+      this.path = path;
+    }
+
+    @Override
+    public BatchedEntries<PathBasedCacheDescriptor> makeRequest(
+        Long nextKey) throws IOException {
+      return namesystem.listPathBasedCacheDescriptors(nextKey, pool, path);
+    }
+
+    @Override
+    public Long elementToPrevKey(PathBasedCacheDescriptor entry) {
+      return entry.getEntryId();
+    }
+  }
+  
+  @Override
+  public RemoteIterator<PathBasedCacheDescriptor> listPathBasedCacheDescriptors(long prevId,
+      String pool, String path) throws IOException {
+    return new ServerSidePathBasedCacheEntriesIterator(prevId, pool, path);
+  }
+
+  @Override
+  public void addCachePool(CachePoolInfo info) throws IOException {
+    namesystem.addCachePool(info);
+  }
+
+  @Override
+  public void modifyCachePool(CachePoolInfo info) throws IOException {
+    namesystem.modifyCachePool(info);
+  }
+
+  @Override
+  public void removeCachePool(String cachePoolName) throws IOException {
+    namesystem.removeCachePool(cachePoolName);
+  }
+
+  private class ServerSideCachePoolIterator 
+      extends BatchedRemoteIterator<String, CachePoolInfo> {
+
+    public ServerSideCachePoolIterator(String prevKey) {
+      super(prevKey);
+    }
+
+    @Override
+    public BatchedEntries<CachePoolInfo> makeRequest(String prevKey)
+        throws IOException {
+      return namesystem.listCachePools(prevKey);
+    }
+
+    @Override
+    public String elementToPrevKey(CachePoolInfo element) {
+      return element.getPoolName();
+    }
+  }
+
+  @Override
+  public RemoteIterator<CachePoolInfo> listCachePools(String prevKey)
+      throws IOException {
+    return new ServerSideCachePoolIterator(prevKey);
+  }
 }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/metrics/NameNodeMetrics.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/metrics/NameNodeMetrics.java
index 9aac83d..c0a204e 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/metrics/NameNodeMetrics.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/metrics/NameNodeMetrics.java
@@ -79,6 +79,8 @@
   MutableCounterLong transactionsBatchedInSync;
   @Metric("Block report") MutableRate blockReport;
   MutableQuantiles[] blockReportQuantiles;
+  @Metric("Cache report") MutableRate cacheReport;
+  MutableQuantiles[] cacheReportQuantiles;
 
   @Metric("Duration in SafeMode at startup in msec")
   MutableGaugeInt safeModeTime;
@@ -91,6 +93,7 @@
     final int len = intervals.length;
     syncsQuantiles = new MutableQuantiles[len];
     blockReportQuantiles = new MutableQuantiles[len];
+    cacheReportQuantiles = new MutableQuantiles[len];
     
     for (int i = 0; i < len; i++) {
       int interval = intervals[i];
@@ -100,6 +103,9 @@
       blockReportQuantiles[i] = registry.newQuantiles(
           "blockReport" + interval + "s", 
           "Block report", "ops", "latency", interval);
+      cacheReportQuantiles[i] = registry.newQuantiles(
+          "cacheReport" + interval + "s",
+          "Cache report", "ops", "latency", interval);
     }
   }
 
@@ -229,6 +235,13 @@
     }
   }
 
+  public void addCacheBlockReport(long latency) {
+    cacheReport.add(latency);
+    for (MutableQuantiles q : cacheReportQuantiles) {
+      q.add(latency);
+    }
+  }
+
   public void setSafeModeTime(long elapsed) {
     safeModeTime.set((int) elapsed);
   }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/startupprogress/StepType.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/startupprogress/StepType.java
index 2ef9c8e..1b43d6a 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/startupprogress/StepType.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/startupprogress/StepType.java
@@ -42,7 +42,17 @@
   /**
    * The namenode is performing an operation related to inodes.
    */
-  INODES("Inodes", "inodes");
+  INODES("Inodes", "inodes"),
+
+  /**
+   * The namenode is performing an operation related to cache pools.
+   */
+  CACHE_POOLS("CachePools", "cache pools"),
+
+  /**
+   * The namenode is performing an operation related to cache entries.
+   */
+  CACHE_ENTRIES("CacheEntries", "cache entries");
 
   private final String name, description;
 
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/protocol/BlockIdCommand.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/protocol/BlockIdCommand.java
new file mode 100644
index 0000000..f4837a1
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/protocol/BlockIdCommand.java
@@ -0,0 +1,50 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.server.protocol;
+
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+
+/****************************************************
+ * A BlockIdCommand is an instruction to a datanode 
+ * regarding some blocks under its control.
+ ****************************************************/
+@InterfaceAudience.Private
+@InterfaceStability.Evolving
+public class BlockIdCommand extends DatanodeCommand {
+  final String poolId;
+  final long blockIds[];
+
+  /**
+   * Create BlockCommand for the given action
+   * @param blocks blocks related to the action
+   */
+  public BlockIdCommand(int action, String poolId, long[] blockIds) {
+    super(action);
+    this.poolId = poolId;
+    this.blockIds= blockIds;
+  }
+  
+  public String getBlockPoolId() {
+    return poolId;
+  }
+  
+  public long[] getBlockIds() {
+    return blockIds;
+  }
+}
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/protocol/DatanodeProtocol.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/protocol/DatanodeProtocol.java
index 27a1099..c990b37 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/protocol/DatanodeProtocol.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/protocol/DatanodeProtocol.java
@@ -19,13 +19,14 @@
 package org.apache.hadoop.hdfs.server.protocol;
 
 import java.io.*;
+import java.util.List;
 
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
+import org.apache.hadoop.hdfs.protocol.BlockListAsLongs;
 import org.apache.hadoop.hdfs.protocol.DatanodeID;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
 import org.apache.hadoop.hdfs.protocol.LocatedBlock;
-import org.apache.hadoop.io.retry.AtMostOnce;
 import org.apache.hadoop.io.retry.Idempotent;
 import org.apache.hadoop.security.KerberosInfo;
 
@@ -74,6 +75,8 @@
   final static int DNA_RECOVERBLOCK = 6;  // request a block recovery
   final static int DNA_ACCESSKEYUPDATE = 7;  // update access key
   final static int DNA_BALANCERBANDWIDTHUPDATE = 8; // update balancer bandwidth
+  final static int DNA_CACHE = 9;      // cache blocks
+  final static int DNA_UNCACHE = 10;   // uncache blocks
 
   /** 
    * Register Datanode.
@@ -104,6 +107,8 @@
   @Idempotent
   public HeartbeatResponse sendHeartbeat(DatanodeRegistration registration,
                                        StorageReport[] reports,
+                                       long dnCacheCapacity,
+                                       long dnCacheUsed,
                                        int xmitsInProgress,
                                        int xceiverCount,
                                        int failedVolumes) throws IOException;
@@ -128,6 +133,24 @@
   public DatanodeCommand blockReport(DatanodeRegistration registration,
       String poolId, StorageBlockReport[] reports) throws IOException;
     
+
+  /**
+   * Communicates the complete list of locally cached blocks to the NameNode.
+   * 
+   * This method is similar to
+   * {@link #blockReport(DatanodeRegistration, String, StorageBlockReport[])},
+   * which is used to communicated blocks stored on disk.
+   *
+   * @param            The datanode registration.
+   * @param poolId     The block pool ID for the blocks.
+   * @param blockIds   A list of block IDs.
+   * @return           The DatanodeCommand.
+   * @throws IOException
+   */
+  @Idempotent
+  public DatanodeCommand cacheReport(DatanodeRegistration registration,
+      String poolId, List<Long> blockIds) throws IOException;
+
   /**
    * blockReceivedAndDeleted() allows the DataNode to tell the NameNode about
    * recently-received and -deleted block data. 
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/CacheAdmin.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/CacheAdmin.java
new file mode 100644
index 0000000..40af431
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/CacheAdmin.java
@@ -0,0 +1,775 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.tools;
+
+import java.io.IOException;
+import java.util.LinkedList;
+import java.util.List;
+
+import org.apache.commons.lang.WordUtils;
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.conf.Configured;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.fs.RemoteIterator;
+import org.apache.hadoop.fs.permission.FsPermission;
+import org.apache.hadoop.hdfs.DistributedFileSystem;
+import org.apache.hadoop.hdfs.protocol.AddPathBasedCacheDirectiveException;
+import org.apache.hadoop.hdfs.protocol.CachePoolInfo;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDescriptor;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDirective;
+import org.apache.hadoop.hdfs.protocol.RemovePathBasedCacheDescriptorException;
+import org.apache.hadoop.hdfs.server.namenode.CachePool;
+import org.apache.hadoop.hdfs.tools.TableListing.Justification;
+import org.apache.hadoop.ipc.RemoteException;
+import org.apache.hadoop.security.UserGroupInformation;
+import org.apache.hadoop.util.StringUtils;
+import org.apache.hadoop.util.Tool;
+
+import com.google.common.base.Joiner;
+
+/**
+ * This class implements command-line operations on the HDFS Cache.
+ */
+@InterfaceAudience.Private
+public class CacheAdmin extends Configured implements Tool {
+
+  /**
+   * Maximum length for printed lines
+   */
+  private static final int MAX_LINE_WIDTH = 80;
+
+  public CacheAdmin() {
+    this(null);
+  }
+
+  public CacheAdmin(Configuration conf) {
+    super(conf);
+  }
+
+  @Override
+  public int run(String[] args) throws IOException {
+    if (args.length == 0) {
+      printUsage(false);
+      return 1;
+    }
+    Command command = determineCommand(args[0]);
+    if (command == null) {
+      System.err.println("Can't understand command '" + args[0] + "'");
+      if (!args[0].startsWith("-")) {
+        System.err.println("Command names must start with dashes.");
+      }
+      printUsage(false);
+      return 1;
+    }
+    List<String> argsList = new LinkedList<String>();
+    for (int j = 1; j < args.length; j++) {
+      argsList.add(args[j]);
+    }
+    return command.run(getConf(), argsList);
+  }
+
+  public static void main(String[] argsArray) throws IOException {
+    CacheAdmin cacheAdmin = new CacheAdmin(new Configuration());
+    System.exit(cacheAdmin.run(argsArray));
+  }
+
+  private static DistributedFileSystem getDFS(Configuration conf)
+      throws IOException {
+    FileSystem fs = FileSystem.get(conf);
+    if (!(fs instanceof DistributedFileSystem)) {
+      throw new IllegalArgumentException("FileSystem " + fs.getUri() + 
+      " is not an HDFS file system");
+    }
+    return (DistributedFileSystem)fs;
+  }
+
+  /**
+   * NN exceptions contain the stack trace as part of the exception message.
+   * When it's a known error, pretty-print the error and squish the stack trace.
+   */
+  private static String prettifyException(Exception e) {
+    return e.getClass().getSimpleName() + ": "
+        + e.getLocalizedMessage().split("\n")[0];
+  }
+
+  private static TableListing getOptionDescriptionListing() {
+    TableListing listing = new TableListing.Builder()
+    .addField("").addField("", true)
+    .wrapWidth(MAX_LINE_WIDTH).hideHeaders().build();
+    return listing;
+  }
+
+  interface Command {
+    String getName();
+    String getShortUsage();
+    String getLongUsage();
+    int run(Configuration conf, List<String> args) throws IOException;
+  }
+
+  private static class AddPathBasedCacheDirectiveCommand implements Command {
+    @Override
+    public String getName() {
+      return "-addDirective";
+    }
+
+    @Override
+    public String getShortUsage() {
+      return "[" + getName() +
+          " -path <path> -replication <replication> -pool <pool-name>]\n";
+    }
+
+    @Override
+    public String getLongUsage() {
+      TableListing listing = getOptionDescriptionListing();
+      listing.addRow("<path>", "A path to cache. The path can be " +
+          "a directory or a file.");
+      listing.addRow("<replication>", "The cache replication factor to use. " +
+          "Defaults to 1.");
+      listing.addRow("<pool-name>", "The pool to which the directive will be " +
+          "added. You must have write permission on the cache pool "
+          + "in order to add new directives.");
+      return getShortUsage() + "\n" +
+        "Add a new PathBasedCache directive.\n\n" +
+        listing.toString();
+    }
+
+    @Override
+    public int run(Configuration conf, List<String> args) throws IOException {
+      String path = StringUtils.popOptionWithArgument("-path", args);
+      if (path == null) {
+        System.err.println("You must specify a path with -path.");
+        return 1;
+      }
+      short replication = 1;
+      String replicationString =
+          StringUtils.popOptionWithArgument("-replication", args);
+      if (replicationString != null) {
+        replication = Short.parseShort(replicationString);
+      }
+      String poolName = StringUtils.popOptionWithArgument("-pool", args);
+      if (poolName == null) {
+        System.err.println("You must specify a pool name with -pool.");
+        return 1;
+      }
+      if (!args.isEmpty()) {
+        System.err.println("Can't understand argument: " + args.get(0));
+        return 1;
+      }
+        
+      DistributedFileSystem dfs = getDFS(conf);
+      PathBasedCacheDirective directive = new PathBasedCacheDirective.Builder().
+          setPath(new Path(path)).
+          setReplication(replication).
+          setPool(poolName).
+          build();
+      try {
+        PathBasedCacheDescriptor descriptor =
+            dfs.addPathBasedCacheDirective(directive);
+        System.out.println("Added PathBasedCache entry "
+            + descriptor.getEntryId());
+      } catch (AddPathBasedCacheDirectiveException e) {
+        System.err.println(prettifyException(e));
+        return 2;
+      }
+
+      return 0;
+    }
+  }
+
+  private static class RemovePathBasedCacheDirectiveCommand implements Command {
+    @Override
+    public String getName() {
+      return "-removeDirective";
+    }
+
+    @Override
+    public String getShortUsage() {
+      return "[" + getName() + " <id>]\n";
+    }
+
+    @Override
+    public String getLongUsage() {
+      TableListing listing = getOptionDescriptionListing();
+      listing.addRow("<id>", "The id of the cache directive to remove.  " + 
+        "You must have write permission on the pool of the " +
+        "directive in order to remove it.  To see a list " +
+        "of PathBasedCache directive IDs, use the -listDirectives command.");
+      return getShortUsage() + "\n" +
+        "Remove a cache directive.\n\n" +
+        listing.toString();
+    }
+
+    @Override
+    public int run(Configuration conf, List<String> args) throws IOException {
+      String idString= StringUtils.popFirstNonOption(args);
+      if (idString == null) {
+        System.err.println("You must specify a directive ID to remove.");
+        return 1;
+      }
+      long id;
+      try {
+        id = Long.valueOf(idString);
+      } catch (NumberFormatException e) {
+        System.err.println("Invalid directive ID " + idString + ": expected " +
+            "a numeric value.");
+        return 1;
+      }
+      if (id <= 0) {
+        System.err.println("Invalid directive ID " + id + ": ids must " +
+            "be greater than 0.");
+        return 1;
+      }
+      if (!args.isEmpty()) {
+        System.err.println("Can't understand argument: " + args.get(0));
+        System.err.println("Usage is " + getShortUsage());
+        return 1;
+      }
+      DistributedFileSystem dfs = getDFS(conf);
+      try {
+        dfs.getClient().removePathBasedCacheDescriptor(id);
+        System.out.println("Removed PathBasedCache directive " + id);
+      } catch (RemovePathBasedCacheDescriptorException e) {
+        System.err.println(prettifyException(e));
+        return 2;
+      }
+      return 0;
+    }
+  }
+
+  private static class RemovePathBasedCacheDirectivesCommand implements Command {
+    @Override
+    public String getName() {
+      return "-removeDirectives";
+    }
+
+    @Override
+    public String getShortUsage() {
+      return "[" + getName() + " <path>]\n";
+    }
+
+    @Override
+    public String getLongUsage() {
+      TableListing listing = getOptionDescriptionListing();
+      listing.addRow("<path>", "The path of the cache directives to remove.  " +
+        "You must have write permission on the pool of the directive in order " +
+        "to remove it.  To see a list of cache directives, use the " +
+        "-listDirectives command.");
+      return getShortUsage() + "\n" +
+        "Remove every cache directive with the specified path.\n\n" +
+        listing.toString();
+    }
+
+    @Override
+    public int run(Configuration conf, List<String> args) throws IOException {
+      String path = StringUtils.popOptionWithArgument("-path", args);
+      if (path == null) {
+        System.err.println("You must specify a path with -path.");
+        return 1;
+      }
+      if (!args.isEmpty()) {
+        System.err.println("Can't understand argument: " + args.get(0));
+        System.err.println("Usage is " + getShortUsage());
+        return 1;
+      }
+      DistributedFileSystem dfs = getDFS(conf);
+      RemoteIterator<PathBasedCacheDescriptor> iter =
+          dfs.listPathBasedCacheDescriptors(null, new Path(path));
+      int exitCode = 0;
+      while (iter.hasNext()) {
+        PathBasedCacheDescriptor entry = iter.next();
+        try {
+          dfs.removePathBasedCacheDescriptor(entry);
+          System.out.println("Removed PathBasedCache directive " +
+              entry.getEntryId());
+        } catch (RemovePathBasedCacheDescriptorException e) {
+          System.err.println(prettifyException(e));
+          exitCode = 2;
+        }
+      }
+      if (exitCode == 0) {
+        System.out.println("Removed every PathBasedCache directive with path " +
+            path);
+      }
+      return exitCode;
+    }
+  }
+
+  private static class ListPathBasedCacheDirectiveCommand implements Command {
+    @Override
+    public String getName() {
+      return "-listDirectives";
+    }
+
+    @Override
+    public String getShortUsage() {
+      return "[" + getName() + " [-path <path>] [-pool <pool>]]\n";
+    }
+
+    @Override
+    public String getLongUsage() {
+      TableListing listing = getOptionDescriptionListing();
+      listing.addRow("<path>", "List only " +
+          "PathBasedCache directives with this path. " +
+          "Note that if there is a PathBasedCache directive for <path> " +
+          "in a cache pool that we don't have read access for, it " + 
+          "will not be listed.");
+      listing.addRow("<pool>", "List only path cache directives in that pool.");
+      return getShortUsage() + "\n" +
+        "List PathBasedCache directives.\n\n" +
+        listing.toString();
+    }
+
+    @Override
+    public int run(Configuration conf, List<String> args) throws IOException {
+      String pathFilter = StringUtils.popOptionWithArgument("-path", args);
+      String poolFilter = StringUtils.popOptionWithArgument("-pool", args);
+      if (!args.isEmpty()) {
+        System.err.println("Can't understand argument: " + args.get(0));
+        return 1;
+      }
+      TableListing tableListing = new TableListing.Builder().
+          addField("ID", Justification.LEFT).
+          addField("POOL", Justification.LEFT).
+          addField("PATH", Justification.LEFT).
+          build();
+      DistributedFileSystem dfs = getDFS(conf);
+      RemoteIterator<PathBasedCacheDescriptor> iter =
+          dfs.listPathBasedCacheDescriptors(poolFilter, pathFilter != null ?
+              new Path(pathFilter) : null);
+      int numEntries = 0;
+      while (iter.hasNext()) {
+        PathBasedCacheDescriptor entry = iter.next();
+        String row[] = new String[] {
+            "" + entry.getEntryId(), entry.getPool(),
+            entry.getPath().toUri().getPath(),
+        };
+        tableListing.addRow(row);
+        numEntries++;
+      }
+      System.out.print(String.format("Found %d entr%s\n",
+          numEntries, numEntries == 1 ? "y" : "ies"));
+      if (numEntries > 0) {
+        System.out.print(tableListing);
+      }
+      return 0;
+    }
+  }
+
+  private static class AddCachePoolCommand implements Command {
+
+    private static final String NAME = "-addPool";
+
+    @Override
+    public String getName() {
+      return NAME;
+    }
+
+    @Override
+    public String getShortUsage() {
+      return "[" + NAME + " <name> [-owner <owner>] " +
+          "[-group <group>] [-mode <mode>] [-weight <weight>]]\n";
+    }
+
+    @Override
+    public String getLongUsage() {
+      TableListing listing = getOptionDescriptionListing();
+
+      listing.addRow("<name>", "Name of the new pool.");
+      listing.addRow("<owner>", "Username of the owner of the pool. " +
+          "Defaults to the current user.");
+      listing.addRow("<group>", "Group of the pool. " +
+          "Defaults to the primary group name of the current user.");
+      listing.addRow("<mode>", "UNIX-style permissions for the pool. " +
+          "Permissions are specified in octal, e.g. 0755. " +
+          "By default, this is set to " + String.format("0%03o",
+          FsPermission.getCachePoolDefault().toShort()));
+      listing.addRow("<weight>", "Weight of the pool. " +
+          "This is a relative measure of the importance of the pool used " +
+          "during cache resource management. By default, it is set to " +
+          CachePool.DEFAULT_WEIGHT);
+
+      return getShortUsage() + "\n" +
+          "Add a new cache pool.\n\n" + 
+          listing.toString();
+    }
+
+    @Override
+    public int run(Configuration conf, List<String> args) throws IOException {
+      String owner = StringUtils.popOptionWithArgument("-owner", args);
+      if (owner == null) {
+        owner = UserGroupInformation.getCurrentUser().getShortUserName();
+      }
+      String group = StringUtils.popOptionWithArgument("-group", args);
+      if (group == null) {
+        group = UserGroupInformation.getCurrentUser().getGroupNames()[0];
+      }
+      String modeString = StringUtils.popOptionWithArgument("-mode", args);
+      int mode;
+      if (modeString == null) {
+        mode = FsPermission.getCachePoolDefault().toShort();
+      } else {
+        mode = Integer.parseInt(modeString, 8);
+      }
+      String weightString = StringUtils.popOptionWithArgument("-weight", args);
+      int weight;
+      if (weightString == null) {
+        weight = CachePool.DEFAULT_WEIGHT;
+      } else {
+        weight = Integer.parseInt(weightString);
+      }
+      String name = StringUtils.popFirstNonOption(args);
+      if (name == null) {
+        System.err.println("You must specify a name when creating a " +
+            "cache pool.");
+        return 1;
+      }
+      if (!args.isEmpty()) {
+        System.err.print("Can't understand arguments: " +
+          Joiner.on(" ").join(args) + "\n");
+        System.err.println("Usage is " + getShortUsage());
+        return 1;
+      }
+      DistributedFileSystem dfs = getDFS(conf);
+      CachePoolInfo info = new CachePoolInfo(name).
+          setOwnerName(owner).
+          setGroupName(group).
+          setMode(new FsPermission((short)mode)).
+          setWeight(weight);
+      try {
+        dfs.addCachePool(info);
+      } catch (IOException e) {
+        throw new RemoteException(e.getClass().getName(), e.getMessage());
+      }
+      System.out.println("Successfully added cache pool " + name + ".");
+      return 0;
+    }
+  }
+
+  private static class ModifyCachePoolCommand implements Command {
+
+    @Override
+    public String getName() {
+      return "-modifyPool";
+    }
+
+    @Override
+    public String getShortUsage() {
+      return "[" + getName() + " <name> [-owner <owner>] " +
+          "[-group <group>] [-mode <mode>] [-weight <weight>]]\n";
+    }
+
+    @Override
+    public String getLongUsage() {
+      TableListing listing = getOptionDescriptionListing();
+
+      listing.addRow("<name>", "Name of the pool to modify.");
+      listing.addRow("<owner>", "Username of the owner of the pool");
+      listing.addRow("<group>", "Groupname of the group of the pool.");
+      listing.addRow("<mode>", "Unix-style permissions of the pool in octal.");
+      listing.addRow("<weight>", "Weight of the pool.");
+
+      return getShortUsage() + "\n" +
+          WordUtils.wrap("Modifies the metadata of an existing cache pool. " +
+          "See usage of " + AddCachePoolCommand.NAME + " for more details",
+          MAX_LINE_WIDTH) + "\n\n" +
+          listing.toString();
+    }
+
+    @Override
+    public int run(Configuration conf, List<String> args) throws IOException {
+      String owner = StringUtils.popOptionWithArgument("-owner", args);
+      String group = StringUtils.popOptionWithArgument("-group", args);
+      String modeString = StringUtils.popOptionWithArgument("-mode", args);
+      Integer mode = (modeString == null) ?
+          null : Integer.parseInt(modeString, 8);
+      String weightString = StringUtils.popOptionWithArgument("-weight", args);
+      Integer weight = (weightString == null) ?
+          null : Integer.parseInt(weightString);
+      String name = StringUtils.popFirstNonOption(args);
+      if (name == null) {
+        System.err.println("You must specify a name when creating a " +
+            "cache pool.");
+        return 1;
+      }
+      if (!args.isEmpty()) {
+        System.err.print("Can't understand arguments: " +
+          Joiner.on(" ").join(args) + "\n");
+        System.err.println("Usage is " + getShortUsage());
+        return 1;
+      }
+      boolean changed = false;
+      CachePoolInfo info = new CachePoolInfo(name);
+      if (owner != null) {
+        info.setOwnerName(owner);
+        changed = true;
+      }
+      if (group != null) {
+        info.setGroupName(group);
+        changed = true;
+      }
+      if (mode != null) {
+        info.setMode(new FsPermission(mode.shortValue()));
+        changed = true;
+      }
+      if (weight != null) {
+        info.setWeight(weight);
+        changed = true;
+      }
+      if (!changed) {
+        System.err.println("You must specify at least one attribute to " +
+            "change in the cache pool.");
+        return 1;
+      }
+      DistributedFileSystem dfs = getDFS(conf);
+      try {
+        dfs.modifyCachePool(info);
+      } catch (IOException e) {
+        throw new RemoteException(e.getClass().getName(), e.getMessage());
+      }
+      System.out.print("Successfully modified cache pool " + name);
+      String prefix = " to have ";
+      if (owner != null) {
+        System.out.print(prefix + "owner name " + owner);
+        prefix = " and ";
+      }
+      if (group != null) {
+        System.out.print(prefix + "group name " + group);
+        prefix = " and ";
+      }
+      if (mode != null) {
+        System.out.print(prefix + "mode " + new FsPermission(mode.shortValue()));
+        prefix = " and ";
+      }
+      if (weight != null) {
+        System.out.print(prefix + "weight " + weight);
+        prefix = " and ";
+      }
+      System.out.print("\n");
+      return 0;
+    }
+  }
+
+  private static class RemoveCachePoolCommand implements Command {
+
+    @Override
+    public String getName() {
+      return "-removePool";
+    }
+
+    @Override
+    public String getShortUsage() {
+      return "[" + getName() + " <name>]\n";
+    }
+
+    @Override
+    public String getLongUsage() {
+      return getShortUsage() + "\n" +
+          WordUtils.wrap("Remove a cache pool. This also uncaches paths " +
+              "associated with the pool.\n\n", MAX_LINE_WIDTH) +
+          "<name>  Name of the cache pool to remove.\n";
+    }
+
+    @Override
+    public int run(Configuration conf, List<String> args) throws IOException {
+      String name = StringUtils.popFirstNonOption(args);
+      if (name == null) {
+        System.err.println("You must specify a name when deleting a " +
+            "cache pool.");
+        return 1;
+      }
+      if (!args.isEmpty()) {
+        System.err.print("Can't understand arguments: " +
+          Joiner.on(" ").join(args) + "\n");
+        System.err.println("Usage is " + getShortUsage());
+        return 1;
+      }
+      DistributedFileSystem dfs = getDFS(conf);
+      try {
+        dfs.removeCachePool(name);
+      } catch (IOException e) {
+        throw new RemoteException(e.getClass().getName(), e.getMessage());
+      }
+      System.out.println("Successfully removed cache pool " + name + ".");
+      return 0;
+    }
+  }
+
+  private static class ListCachePoolsCommand implements Command {
+
+    @Override
+    public String getName() {
+      return "-listPools";
+    }
+
+    @Override
+    public String getShortUsage() {
+      return "[" + getName() + " [name]]\n";
+    }
+
+    @Override
+    public String getLongUsage() {
+      TableListing listing = getOptionDescriptionListing();
+      listing.addRow("[name]", "If specified, list only the named cache pool.");
+
+      return getShortUsage() + "\n" +
+          WordUtils.wrap("Display information about one or more cache pools, " +
+              "e.g. name, owner, group, permissions, etc.", MAX_LINE_WIDTH) +
+          "\n\n" +
+          listing.toString();
+    }
+
+    @Override
+    public int run(Configuration conf, List<String> args) throws IOException {
+      String name = StringUtils.popFirstNonOption(args);
+      if (!args.isEmpty()) {
+        System.err.print("Can't understand arguments: " +
+          Joiner.on(" ").join(args) + "\n");
+        System.err.println("Usage is " + getShortUsage());
+        return 1;
+      }
+      DistributedFileSystem dfs = getDFS(conf);
+      TableListing listing = new TableListing.Builder().
+          addField("NAME", Justification.LEFT).
+          addField("OWNER", Justification.LEFT).
+          addField("GROUP", Justification.LEFT).
+          addField("MODE", Justification.LEFT).
+          addField("WEIGHT", Justification.LEFT).
+          build();
+      int numResults = 0;
+      try {
+        RemoteIterator<CachePoolInfo> iter = dfs.listCachePools();
+        while (iter.hasNext()) {
+          CachePoolInfo info = iter.next();
+          if (name == null || info.getPoolName().equals(name)) {
+            listing.addRow(new String[] {
+                info.getPoolName(),
+                info.getOwnerName(),
+                info.getGroupName(),
+                info.getMode().toString(),
+                info.getWeight().toString(),
+            });
+            ++numResults;
+            if (name != null) {
+              break;
+            }
+          }
+        }
+      } catch (IOException e) {
+        throw new RemoteException(e.getClass().getName(), e.getMessage());
+      }
+      System.out.print(String.format("Found %d result%s.\n", numResults,
+          (numResults == 1 ? "" : "s")));
+      if (numResults > 0) { 
+        System.out.print(listing);
+      }
+      // If there are no results, we return 1 (failure exit code);
+      // otherwise we return 0 (success exit code).
+      return (numResults == 0) ? 1 : 0;
+    }
+  }
+
+  private static class HelpCommand implements Command {
+    @Override
+    public String getName() {
+      return "-help";
+    }
+
+    @Override
+    public String getShortUsage() {
+      return "[-help <command-name>]\n";
+    }
+
+    @Override
+    public String getLongUsage() {
+      TableListing listing = getOptionDescriptionListing();
+      listing.addRow("<command-name>", "The command for which to get " +
+          "detailed help. If no command is specified, print detailed help for " +
+          "all commands");
+      return getShortUsage() + "\n" +
+        "Get detailed help about a command.\n\n" +
+        listing.toString();
+    }
+
+    @Override
+    public int run(Configuration conf, List<String> args) throws IOException {
+      if (args.size() == 0) {
+        for (Command command : COMMANDS) {
+          System.err.println(command.getLongUsage());
+        }
+        return 0;
+      }
+      if (args.size() != 1) {
+        System.out.println("You must give exactly one argument to -help.");
+        return 0;
+      }
+      String commandName = args.get(0);
+      commandName = commandName.replaceAll("^[-]*", "");
+      Command command = determineCommand(commandName);
+      if (command == null) {
+        System.err.print("Sorry, I don't know the command '" +
+          commandName + "'.\n");
+        System.err.print("Valid command names are:\n");
+        String separator = "";
+        for (Command c : COMMANDS) {
+          System.err.print(separator + c.getName());
+          separator = ", ";
+        }
+        System.err.print("\n");
+        return 1;
+      }
+      System.err.print(command.getLongUsage());
+      return 0;
+    }
+  }
+
+  private static Command[] COMMANDS = {
+    new AddPathBasedCacheDirectiveCommand(),
+    new RemovePathBasedCacheDirectiveCommand(),
+    new RemovePathBasedCacheDirectivesCommand(),
+    new ListPathBasedCacheDirectiveCommand(),
+    new AddCachePoolCommand(),
+    new ModifyCachePoolCommand(),
+    new RemoveCachePoolCommand(),
+    new ListCachePoolsCommand(),
+    new HelpCommand(),
+  };
+
+  private static void printUsage(boolean longUsage) {
+    System.err.println(
+        "Usage: bin/hdfs cacheadmin [COMMAND]");
+    for (Command command : COMMANDS) {
+      if (longUsage) {
+        System.err.print(command.getLongUsage());
+      } else {
+        System.err.print("          " + command.getShortUsage());
+      }
+    }
+    System.err.println();
+  }
+
+  private static Command determineCommand(String commandName) {
+    for (int i = 0; i < COMMANDS.length; i++) {
+      if (COMMANDS[i].getName().equals(commandName)) {
+        return COMMANDS[i];
+      }
+    }
+    return null;
+  }
+}
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/TableListing.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/TableListing.java
new file mode 100644
index 0000000..4d807cb
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/TableListing.java
@@ -0,0 +1,281 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.tools;
+
+import java.util.ArrayList;
+import java.util.LinkedList;
+
+import org.apache.commons.lang.StringUtils;
+import org.apache.commons.lang.WordUtils;
+import org.apache.hadoop.classification.InterfaceAudience;
+
+/**
+ * This class implements a "table listing" with column headers.
+ * 
+ * Example:
+ * 
+ * NAME   OWNER   GROUP   MODE       WEIGHT
+ * pool1  andrew  andrew  rwxr-xr-x  100
+ * pool2  andrew  andrew  rwxr-xr-x  100
+ * pool3  andrew  andrew  rwxr-xr-x  100
+ * 
+ */
+@InterfaceAudience.Private
+public class TableListing {
+  public enum Justification {
+    LEFT,
+    RIGHT;
+  }
+
+  private static class Column {
+    private final ArrayList<String> rows;
+    private final Justification justification;
+    private final boolean wrap;
+
+    private int wrapWidth = Integer.MAX_VALUE;
+    private int maxWidth;
+
+    Column(String title, Justification justification, boolean wrap) {
+      this.rows = new ArrayList<String>();
+      this.justification = justification;
+      this.wrap = wrap;
+      this.maxWidth = 0;
+      addRow(title);
+    }
+
+    private void addRow(String val) {
+      if ((val.length() + 1) > maxWidth) {
+        maxWidth = val.length() + 1;
+      }
+      // Ceiling at wrapWidth, because it'll get wrapped
+      if (maxWidth > wrapWidth) {
+        maxWidth = wrapWidth;
+      }
+      rows.add(val);
+    }
+
+    private int getMaxWidth() {
+      return maxWidth;
+    }
+
+    private void setWrapWidth(int width) {
+      wrapWidth = width;
+      // Ceiling the maxLength at wrapWidth
+      if (maxWidth > wrapWidth) {
+        maxWidth = wrapWidth;
+      }
+      // Else we need to traverse through and find the real maxWidth
+      else {
+        maxWidth = 0;
+        for (int i=0; i<rows.size(); i++) {
+          int length = rows.get(i).length();
+          if (length > maxWidth) {
+            maxWidth = length;
+          }
+        }
+      }
+    }
+
+    /**
+     * Return the ith row of the column as a set of wrapped strings, each at
+     * most wrapWidth in length.
+     */
+    String[] getRow(int idx) {
+      String raw = rows.get(idx);
+      // Line-wrap if it's too long
+      String[] lines = new String[] {raw};
+      if (wrap) {
+        lines = WordUtils.wrap(lines[0], wrapWidth, "\n", true).split("\n");
+      }
+      for (int i=0; i<lines.length; i++) {
+        if (justification == Justification.LEFT) {
+          lines[i] = StringUtils.rightPad(lines[i], maxWidth);
+        } else if (justification == Justification.RIGHT) {
+          lines[i] = StringUtils.leftPad(lines[i], maxWidth);
+        }
+      }
+      return lines;
+    }
+  }
+
+  public static class Builder {
+    private final LinkedList<Column> columns = new LinkedList<Column>();
+    private boolean showHeader = true;
+    private int wrapWidth = Integer.MAX_VALUE;
+
+    /**
+     * Create a new Builder.
+     */
+    public Builder() {
+    }
+
+    public Builder addField(String title) {
+      return addField(title, Justification.LEFT, false);
+    }
+
+    public Builder addField(String title, Justification justification) {
+      return addField(title, justification, false);
+    }
+
+    public Builder addField(String title, boolean wrap) {
+      return addField(title, Justification.LEFT, wrap);
+    }
+
+    /**
+     * Add a new field to the Table under construction.
+     * 
+     * @param title Field title.
+     * @param justification Right or left justification. Defaults to left.
+     * @param wrap Width at which to auto-wrap the content of the cell.
+     *        Defaults to Integer.MAX_VALUE.
+     * @return This Builder object
+     */
+    public Builder addField(String title, Justification justification, 
+        boolean wrap) {
+      columns.add(new Column(title, justification, wrap));
+      return this;
+    }
+
+    /**
+     * Whether to hide column headers in table output
+     */
+    public Builder hideHeaders() {
+      this.showHeader = false;
+      return this;
+    }
+
+    /**
+     * Whether to show column headers in table output. This is the default.
+     */
+    public Builder showHeaders() {
+      this.showHeader = true;
+      return this;
+    }
+
+    /**
+     * Set the maximum width of a row in the TableListing. Must have one or
+     * more wrappable fields for this to take effect.
+     */
+    public Builder wrapWidth(int width) {
+      this.wrapWidth = width;
+      return this;
+    }
+
+    /**
+     * Create a new TableListing.
+     */
+    public TableListing build() {
+      return new TableListing(columns.toArray(new Column[0]), showHeader,
+          wrapWidth);
+    }
+  }
+
+  private final Column columns[];
+
+  private int numRows;
+  private boolean showHeader;
+  private int wrapWidth;
+
+  TableListing(Column columns[], boolean showHeader, int wrapWidth) {
+    this.columns = columns;
+    this.numRows = 0;
+    this.showHeader = showHeader;
+    this.wrapWidth = wrapWidth;
+  }
+
+  /**
+   * Add a new row.
+   *
+   * @param row    The row of objects to add-- one per column.
+   */
+  public void addRow(String... row) {
+    if (row.length != columns.length) {
+      throw new RuntimeException("trying to add a row with " + row.length +
+            " columns, but we have " + columns.length + " columns.");
+    }
+    for (int i = 0; i < columns.length; i++) {
+      columns[i].addRow(row[i]);
+    }
+    numRows++;
+  }
+
+  @Override
+  public String toString() {
+    StringBuilder builder = new StringBuilder();
+    // Calculate the widths of each column based on their maxWidths and
+    // the wrapWidth for the entire table
+    int width = (columns.length-1)*2; // inter-column padding
+    for (int i=0; i<columns.length; i++) {
+      width += columns[i].maxWidth;
+    }
+    // Decrease the column size of wrappable columns until the goal width
+    // is reached, or we can't decrease anymore
+    while (width > wrapWidth) {
+      boolean modified = false;
+      for (int i=0; i<columns.length; i++) {
+        Column column = columns[i];
+        if (column.wrap) {
+          int maxWidth = column.getMaxWidth();
+          if (maxWidth > 4) {
+            column.setWrapWidth(maxWidth-1);
+            modified = true;
+            width -= 1;
+            if (width <= wrapWidth) {
+              break;
+            }
+          }
+        }
+      }
+      if (!modified) {
+        break;
+      }
+    }
+
+    int startrow = 0;
+    if (!showHeader) {
+      startrow = 1;
+    }
+    String[][] columnLines = new String[columns.length][];
+    for (int i = startrow; i < numRows + 1; i++) {
+      int maxColumnLines = 0;
+      for (int j = 0; j < columns.length; j++) {
+        columnLines[j] = columns[j].getRow(i);
+        if (columnLines[j].length > maxColumnLines) {
+          maxColumnLines = columnLines[j].length;
+        }
+      }
+
+      for (int c = 0; c < maxColumnLines; c++) {
+        // First column gets no left-padding
+        String prefix = "";
+        for (int j = 0; j < columns.length; j++) {
+          // Prepend padding
+          builder.append(prefix);
+          prefix = " ";
+          if (columnLines[j].length > c) {
+            builder.append(columnLines[j][c]);
+          } else {
+            builder.append(StringUtils.repeat(" ", columns[j].maxWidth));
+          }
+        }
+        builder.append("\n");
+      }
+    }
+    return builder.toString();
+  }
+}
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineImageViewer/ImageLoaderCurrent.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineImageViewer/ImageLoaderCurrent.java
index d23b27b..25b128d 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineImageViewer/ImageLoaderCurrent.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineImageViewer/ImageLoaderCurrent.java
@@ -126,7 +126,7 @@
                                       new SimpleDateFormat("yyyy-MM-dd HH:mm");
   private static int[] versions = { -16, -17, -18, -19, -20, -21, -22, -23,
       -24, -25, -26, -27, -28, -30, -31, -32, -33, -34, -35, -36, -37, -38, -39,
-      -40, -41, -42, -43, -44, -45, -46, -47 };
+      -40, -41, -42, -43, -44, -45, -46, -47, -48 };
   private int imageVersion = 0;
   
   private final Map<Long, String> subtreeMap = new HashMap<Long, String>();
@@ -216,6 +216,9 @@
         processDelegationTokens(in, v);
       }
       
+      if (LayoutVersion.supports(Feature.CACHING, imageVersion)) {
+        processCacheManagerState(in, v);
+      }
       v.leaveEnclosingElement(); // FSImage
       done = true;
     } finally {
@@ -228,6 +231,25 @@
   }
 
   /**
+   * Process CacheManager state from the fsimage.
+   */
+  private void processCacheManagerState(DataInputStream in, ImageVisitor v)
+      throws IOException {
+    v.visit(ImageElement.CACHE_NEXT_ENTRY_ID, in.readLong());
+    final int numPools = in.readInt();
+    for (int i=0; i<numPools; i++) {
+      v.visit(ImageElement.CACHE_POOL_NAME, Text.readString(in));
+      processCachePoolPermission(in, v);
+      v.visit(ImageElement.CACHE_POOL_WEIGHT, in.readInt());
+    }
+    final int numEntries = in.readInt();
+    for (int i=0; i<numEntries; i++) {
+      v.visit(ImageElement.CACHE_ENTRY_PATH, Text.readString(in));
+      v.visit(ImageElement.CACHE_ENTRY_REPLICATION, in.readShort());
+      v.visit(ImageElement.CACHE_ENTRY_POOL_NAME, Text.readString(in));
+    }
+  }
+  /**
    * Process the Delegation Token related section in fsimage.
    * 
    * @param in DataInputStream to process
@@ -385,6 +407,22 @@
   }
 
   /**
+   * Extract CachePool permissions stored in the fsimage file.
+   *
+   * @param in Datastream to process
+   * @param v Visitor to walk over inodes
+   */
+  private void processCachePoolPermission(DataInputStream in, ImageVisitor v)
+      throws IOException {
+    v.visitEnclosingElement(ImageElement.PERMISSIONS);
+    v.visit(ImageElement.CACHE_POOL_OWNER_NAME, Text.readString(in));
+    v.visit(ImageElement.CACHE_POOL_GROUP_NAME, Text.readString(in));
+    FsPermission fsp = new FsPermission(in.readShort());
+    v.visit(ImageElement.CACHE_POOL_PERMISSION_STRING, fsp.toString());
+    v.leaveEnclosingElement(); // Permissions
+  }
+
+  /**
    * Process the INode records stored in the fsimage.
    *
    * @param in Datastream to process
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineImageViewer/ImageVisitor.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineImageViewer/ImageVisitor.java
index b0c2bb9..8914bcf 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineImageViewer/ImageVisitor.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/offlineImageViewer/ImageVisitor.java
@@ -117,7 +117,19 @@
     SNAPSHOT_DST_SNAPSHOT_ID,
     SNAPSHOT_LAST_SNAPSHOT_ID,
     SNAPSHOT_REF_INODE_ID,
-    SNAPSHOT_REF_INODE
+    SNAPSHOT_REF_INODE,
+
+    CACHE_NEXT_ENTRY_ID,
+    CACHE_NUM_POOLS,
+    CACHE_POOL_NAME,
+    CACHE_POOL_OWNER_NAME,
+    CACHE_POOL_GROUP_NAME,
+    CACHE_POOL_PERMISSION_STRING,
+    CACHE_POOL_WEIGHT,
+    CACHE_NUM_ENTRIES,
+    CACHE_ENTRY_PATH,
+    CACHE_ENTRY_REPLICATION,
+    CACHE_ENTRY_POOL_NAME
   }
   
   /**
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/web/JsonUtil.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/web/JsonUtil.java
index db4adc5..ab24fbe 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/web/JsonUtil.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/web/JsonUtil.java
@@ -289,6 +289,8 @@
     m.put("dfsUsed", datanodeinfo.getDfsUsed());
     m.put("remaining", datanodeinfo.getRemaining());
     m.put("blockPoolUsed", datanodeinfo.getBlockPoolUsed());
+    m.put("cacheCapacity", datanodeinfo.getCacheCapacity());
+    m.put("cacheUsed", datanodeinfo.getCacheUsed());
     m.put("lastUpdate", datanodeinfo.getLastUpdate());
     m.put("xceiverCount", datanodeinfo.getXceiverCount());
     m.put("networkLocation", datanodeinfo.getNetworkLocation());
@@ -296,16 +298,36 @@
     return m;
   }
 
+  private static int getInt(Map<?, ?> m, String key, final int defaultValue) {
+    Object value = m.get(key);
+    if (value == null) {
+      return defaultValue;
+    }
+    return (int) (long) (Long) value;
+  }
+
+  private static long getLong(Map<?, ?> m, String key, final long defaultValue) {
+    Object value = m.get(key);
+    if (value == null) {
+      return defaultValue;
+    }
+    return (long) (Long) value;
+  }
+
+  private static String getString(Map<?, ?> m, String key,
+      final String defaultValue) {
+    Object value = m.get(key);
+    if (value == null) {
+      return defaultValue;
+    }
+    return (String) value;
+  }
+
   /** Convert a Json map to an DatanodeInfo object. */
   static DatanodeInfo toDatanodeInfo(final Map<?, ?> m) {
     if (m == null) {
       return null;
     }
-    
-    Object infoSecurePort = m.get("infoSecurePort");
-    if (infoSecurePort == null) {
-      infoSecurePort = 0l; // same as the default value in hdfs.proto
-    }
 
     return new DatanodeInfo(
         (String)m.get("ipAddr"),
@@ -313,17 +335,19 @@
         (String)m.get("storageID"),
         (int)(long)(Long)m.get("xferPort"),
         (int)(long)(Long)m.get("infoPort"),
-        (int)(long)(Long)infoSecurePort,
+        getInt(m, "infoSecurePort", 0),
         (int)(long)(Long)m.get("ipcPort"),
 
-        (Long)m.get("capacity"),
-        (Long)m.get("dfsUsed"),
-        (Long)m.get("remaining"),
-        (Long)m.get("blockPoolUsed"),
-        (Long)m.get("lastUpdate"),
-        (int)(long)(Long)m.get("xceiverCount"),
-        (String)m.get("networkLocation"),
-        AdminStates.valueOf((String)m.get("adminState")));
+        getLong(m, "capacity", 0l),
+        getLong(m, "dfsUsed", 0l),
+        getLong(m, "remaining", 0l),
+        getLong(m, "blockPoolUsed", 0l),
+        getLong(m, "cacheCapacity", 0l),
+        getLong(m, "cacheUsed", 0l),
+        getLong(m, "lastUpdate", 0l),
+        getInt(m, "xceiverCount", 0),
+        getString(m, "networkLocation", ""),
+        AdminStates.valueOf(getString(m, "adminState", "NORMAL")));
   }
 
   /** Convert a DatanodeInfo[] to a Json array. */
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/ClientNamenodeProtocol.proto b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/ClientNamenodeProtocol.proto
index 95fcc50..ed122fc 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/ClientNamenodeProtocol.proto
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/ClientNamenodeProtocol.proto
@@ -363,6 +363,91 @@
   required bool result = 1;
 }
 
+message PathBasedCacheDirectiveProto {
+  required string path = 1;
+  required uint32 replication = 2;
+  required string pool = 3;
+}
+
+message AddPathBasedCacheDirectiveRequestProto {
+  required PathBasedCacheDirectiveProto directive = 1;
+}
+
+message AddPathBasedCacheDirectiveResponseProto {
+  required int64 descriptorId = 1;
+}
+
+message RemovePathBasedCacheDescriptorRequestProto {
+  required int64 descriptorId = 1;
+}
+
+message RemovePathBasedCacheDescriptorResponseProto {
+}
+
+message ListPathBasedCacheDescriptorsRequestProto {
+  required int64 prevId = 1;
+  optional string pool = 2;
+  optional string path = 3;
+}
+
+message ListPathBasedCacheDescriptorsElementProto {
+  required int64 id = 1;
+  required string pool = 2;
+  required uint32 replication = 3;
+  required string path = 4;
+}
+
+message ListPathBasedCacheDescriptorsResponseProto {
+  repeated ListPathBasedCacheDescriptorsElementProto elements = 1;
+  required bool hasMore = 2;
+}
+
+message AddCachePoolRequestProto {
+  required string poolName = 1;
+  optional string ownerName = 2;
+  optional string groupName = 3;
+  optional int32 mode = 4;
+  optional int32 weight = 5;
+}
+
+message AddCachePoolResponseProto { // void response
+}
+
+message ModifyCachePoolRequestProto {
+  required string poolName = 1;
+  optional string ownerName = 2;
+  optional string groupName = 3;
+  optional int32 mode = 4;
+  optional int32 weight = 5;
+}
+
+message ModifyCachePoolResponseProto { // void response
+}
+
+message RemoveCachePoolRequestProto {
+  required string poolName = 1;
+}
+
+message RemoveCachePoolResponseProto { // void response
+}
+
+message ListCachePoolsRequestProto {
+  required string prevPoolName = 1;
+}
+
+message ListCachePoolsResponseProto {
+  repeated ListCachePoolsResponseElementProto elements = 1;
+  required bool hasMore = 2;
+}
+
+message ListCachePoolsResponseElementProto {
+  required string poolName = 1;
+  required string ownerName = 2;
+  required string groupName = 3;
+  required int32 mode = 4;
+  required int32 weight = 5;
+}
+
 message GetFileLinkInfoRequestProto {
   required string src = 1;
 }
@@ -544,6 +629,20 @@
       returns(ListCorruptFileBlocksResponseProto);
   rpc metaSave(MetaSaveRequestProto) returns(MetaSaveResponseProto);
   rpc getFileInfo(GetFileInfoRequestProto) returns(GetFileInfoResponseProto);
+  rpc addPathBasedCacheDirective(AddPathBasedCacheDirectiveRequestProto)
+      returns (AddPathBasedCacheDirectiveResponseProto);
+  rpc removePathBasedCacheDescriptor(RemovePathBasedCacheDescriptorRequestProto)
+      returns (RemovePathBasedCacheDescriptorResponseProto);
+  rpc listPathBasedCacheDescriptors(ListPathBasedCacheDescriptorsRequestProto)
+      returns (ListPathBasedCacheDescriptorsResponseProto);
+  rpc addCachePool(AddCachePoolRequestProto)
+      returns(AddCachePoolResponseProto);
+  rpc modifyCachePool(ModifyCachePoolRequestProto)
+      returns(ModifyCachePoolResponseProto);
+  rpc removeCachePool(RemoveCachePoolRequestProto)
+      returns(RemoveCachePoolResponseProto);
+  rpc listCachePools(ListCachePoolsRequestProto)
+      returns(ListCachePoolsResponseProto);
   rpc getFileLinkInfo(GetFileLinkInfoRequestProto)
       returns(GetFileLinkInfoResponseProto);
   rpc getContentSummary(GetContentSummaryRequestProto)
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/DatanodeProtocol.proto b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/DatanodeProtocol.proto
index bc5461b..d64d97a 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/DatanodeProtocol.proto
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/DatanodeProtocol.proto
@@ -70,6 +70,7 @@
     RegisterCommand = 5;
     UnusedUpgradeCommand = 6;
     NullDatanodeCommand = 7;
+    BlockIdCommand = 8;
   }
 
   required Type cmdType = 1;    // Type of the command
@@ -82,6 +83,7 @@
   optional FinalizeCommandProto finalizeCmd = 5;
   optional KeyUpdateCommandProto keyUpdateCmd = 6;
   optional RegisterCommandProto registerCmd = 7;
+  optional BlockIdCommandProto blkIdCmd = 8;
 }
 
 /**
@@ -102,7 +104,7 @@
   enum Action {  
     TRANSFER = 1;   // Transfer blocks to another datanode
     INVALIDATE = 2; // Invalidate blocks
-    SHUTDOWN = 3; // Shutdown the datanode
+    SHUTDOWN = 3;   // Shutdown the datanode
   }
   required Action action = 1;
   required string blockPoolId = 2;
@@ -111,6 +113,20 @@
 }
 
 /**
+ * Command to instruct datanodes to perform certain action
+ * on the given set of block IDs.
+ */
+message BlockIdCommandProto {
+  enum Action {
+    CACHE = 1;
+    UNCACHE = 2;
+  }
+  required Action action = 1;
+  required string blockPoolId = 2;
+  repeated uint64 blockIds = 3 [packed=true];
+}
+
+/**
  * List of blocks to be recovered by the datanode
  */
 message BlockRecoveryCommandProto {
@@ -163,6 +179,8 @@
  * xmitsInProgress - number of transfers from this datanode to others
  * xceiverCount - number of active transceiver threads
  * failedVolumes - number of failed volumes
+ * cacheCapacity - total cache capacity available at the datanode
+ * cacheUsed - amount of cache used
  */
 message HeartbeatRequestProto {
   required DatanodeRegistrationProto registration = 1; // Datanode info
@@ -170,6 +188,8 @@
   optional uint32 xmitsInProgress = 3 [ default = 0 ];
   optional uint32 xceiverCount = 4 [ default = 0 ];
   optional uint32 failedVolumes = 5 [ default = 0 ];
+  optional uint64 dnCacheCapacity = 6 [ default = 0 ];
+  optional uint64 dnCacheUsed = 7 [default = 0 ];
 }
 
 message StorageReportProto {
@@ -202,9 +222,11 @@
 /**
  * registration - datanode registration information
  * blockPoolID  - block pool ID of the reported blocks
- * blocks       - each block is represented as two longs in the array.
+ * blocks       - each block is represented as multiple longs in the array.
  *                first long represents block ID
  *                second long represents length
+ *                third long represents gen stamp
+ *                fourth long (if under construction) represents replica state
  */
 message BlockReportRequestProto {
   required DatanodeRegistrationProto registration = 1;
@@ -228,6 +250,21 @@
 } 
 
 /**
+ * registration - datanode registration information
+ * blockPoolId  - block pool ID of the reported blocks
+ * blocks       - representation of blocks as longs for efficiency reasons
+ */
+message CacheReportRequestProto {
+  required DatanodeRegistrationProto registration = 1;
+  required string blockPoolId = 2;
+  repeated uint64 blocks = 3 [packed=true];
+}
+
+message CacheReportResponseProto {
+  optional DatanodeCommandProto cmd = 1;
+}
+
+/**
  * Data structure to send received or deleted block information
  * from datanode to namenode.
  */
@@ -345,6 +382,11 @@
   rpc blockReport(BlockReportRequestProto) returns(BlockReportResponseProto);
 
   /**
+   * Report cached blocks at a datanode to the namenode
+   */
+  rpc cacheReport(CacheReportRequestProto) returns(CacheReportResponseProto);
+
+  /**
    * Incremental block report from the DN. This contains info about recently
    * received and deleted blocks, as well as when blocks start being
    * received.
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/hdfs.proto b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/hdfs.proto
index 7a9d0ad..3cb8a61 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/hdfs.proto
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/hdfs.proto
@@ -83,6 +83,8 @@
   }
 
   optional AdminState adminState = 10 [default = NORMAL];
+  optional uint64 cacheCapacity = 11 [default = 0];
+  optional uint64 cacheUsed = 12 [default = 0];
 }
 
 /**
@@ -127,6 +129,7 @@
                                         // their locations are not part of this object
 
   required hadoop.common.TokenProto blockToken = 5;
+  repeated bool isCached = 6 [packed=true]; // if a location in locs is cached
 }
 
 message DataEncryptionKeyProto {
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml b/hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml
index 1458095..994bb60 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml
@@ -1459,4 +1459,70 @@
   </description>
 </property>
 
+<property>
+  <name>dfs.namenode.caching.enabled</name>
+  <value>false</value>
+  <description>
+    Set to true to enable block caching.  This flag enables the NameNode to
+    maintain a mapping of cached blocks to DataNodes via processing DataNode
+    cache reports.  Based on these reports and addition and removal of caching
+    directives, the NameNode will schedule caching and uncaching work.
+  </description>
+</property>
+
+<property>
+  <name>dfs.datanode.max.locked.memory</name>
+  <value>0</value>
+  <description>
+    The amount of memory in bytes to use for caching of block replicas in
+    memory on the datanode. The datanode's maximum locked memory soft ulimit
+    (RLIMIT_MEMLOCK) must be set to at least this value, else the datanode
+    will abort on startup.
+
+    By default, this parameter is set to 0, which disables in-memory caching.
+
+    If the native libraries are not available to the DataNode, this
+    configuration has no effect.
+  </description>
+</property>
+
+<property>
+  <name>dfs.namenode.path.based.cache.refresh.interval.ms</name>
+  <value>300000</value>
+  <description>
+    The amount of milliseconds between subsequent path cache rescans.  Path
+    cache rescans are when we calculate which blocks should be cached, and on
+    what datanodes.
+
+    By default, this parameter is set to 300000, which is five minutes.
+  </description>
+</property>
+
+<property>
+  <name>dfs.datanode.fsdatasetcache.max.threads.per.volume</name>
+  <value>4</value>
+  <description>
+    The maximum number of threads per volume to use for caching new data
+    on the datanode. These threads consume both I/O and CPU. This can affect
+    normal datanode operations.
+  </description>
+</property>
+
+<property>
+  <name>dfs.cachereport.intervalMsec</name>
+  <value>10000</value>
+  <description>
+    Determines cache reporting interval in milliseconds.  After this amount of
+    time, the DataNode sends a full report of its cache state to the NameNode.
+    The NameNode uses the cache report to update its map of cached blocks to
+    DataNode locations.
+
+    This configuration has no effect if in-memory caching has been disabled by
+    setting dfs.datanode.max.locked.memory to 0 (which is the default).
+
+    If the native libraries are not available to the DataNode, this
+    configuration has no effect.
+  </description>
+</property>
+
 </configuration>
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/cli/TestCacheAdminCLI.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/cli/TestCacheAdminCLI.java
new file mode 100644
index 0000000..f25c4fe
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/cli/TestCacheAdminCLI.java
@@ -0,0 +1,141 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.cli;
+
+import static org.junit.Assert.assertTrue;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.cli.util.CLICommand;
+import org.apache.hadoop.cli.util.CLICommandCacheAdmin;
+import org.apache.hadoop.cli.util.CLICommandTypes;
+import org.apache.hadoop.cli.util.CLITestCmd;
+import org.apache.hadoop.cli.util.CacheAdminCmdExecutor;
+import org.apache.hadoop.cli.util.CommandExecutor;
+import org.apache.hadoop.cli.util.CommandExecutor.Result;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.hdfs.DFSConfigKeys;
+import org.apache.hadoop.hdfs.DistributedFileSystem;
+import org.apache.hadoop.hdfs.HDFSPolicyProvider;
+import org.apache.hadoop.hdfs.MiniDFSCluster;
+import org.apache.hadoop.hdfs.tools.CacheAdmin;
+import org.apache.hadoop.security.authorize.PolicyProvider;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.xml.sax.SAXException;
+
+public class TestCacheAdminCLI extends CLITestHelper {
+
+  public static final Log LOG = LogFactory.getLog(TestCacheAdminCLI.class);
+
+  protected MiniDFSCluster dfsCluster = null;
+  protected FileSystem fs = null;
+  protected String namenode = null;
+
+  @Before
+  @Override
+  public void setUp() throws Exception {
+    super.setUp();
+    conf.setClass(PolicyProvider.POLICY_PROVIDER_CONFIG,
+        HDFSPolicyProvider.class, PolicyProvider.class);
+
+    // Many of the tests expect a replication value of 1 in the output
+    conf.setInt(DFSConfigKeys.DFS_REPLICATION_KEY, 1);
+
+    dfsCluster = new MiniDFSCluster.Builder(conf).numDataNodes(3).build();
+
+    dfsCluster.waitClusterUp();
+    namenode = conf.get(DFSConfigKeys.FS_DEFAULT_NAME_KEY, "file:///");
+    username = System.getProperty("user.name");
+
+    fs = dfsCluster.getFileSystem();
+    assertTrue("Not a HDFS: "+fs.getUri(),
+               fs instanceof DistributedFileSystem);
+  }
+
+  @After
+  @Override
+  public void tearDown() throws Exception {
+    if (fs != null) {
+      fs.close();
+    }
+    if (dfsCluster != null) {
+      dfsCluster.shutdown();
+    }
+    Thread.sleep(2000);
+    super.tearDown();
+  }
+
+  @Override
+  protected String getTestFile() {
+    return "testCacheAdminConf.xml";
+  }
+
+  @Override
+  protected TestConfigFileParser getConfigParser() {
+    return new TestConfigFileParserCacheAdmin();
+  }
+
+  private class TestConfigFileParserCacheAdmin extends
+      CLITestHelper.TestConfigFileParser {
+    @Override
+    public void endElement(String uri, String localName, String qName)
+        throws SAXException {
+      if (qName.equals("cache-admin-command")) {
+        if (testCommands != null) {
+          testCommands.add(new CLITestCmdCacheAdmin(charString,
+              new CLICommandCacheAdmin()));
+        } else if (cleanupCommands != null) {
+          cleanupCommands.add(new CLITestCmdCacheAdmin(charString,
+              new CLICommandCacheAdmin()));
+        }
+      } else {
+        super.endElement(uri, localName, qName);
+      }
+    }
+  }
+
+  private class CLITestCmdCacheAdmin extends CLITestCmd {
+
+    public CLITestCmdCacheAdmin(String str, CLICommandTypes type) {
+      super(str, type);
+    }
+
+    @Override
+    public CommandExecutor getExecutor(String tag)
+        throws IllegalArgumentException {
+      if (getType() instanceof CLICommandCacheAdmin) {
+        return new CacheAdminCmdExecutor(tag, new CacheAdmin(conf));
+      }
+      return super.getExecutor(tag);
+    }
+  }
+
+  @Override
+  protected Result execute(CLICommand cmd) throws Exception {
+    return cmd.getExecutor("").executeCommand(cmd.getCmd());
+  }
+
+  @Test
+  @Override
+  public void testAll () {
+    super.testAll();
+  }
+}
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/cli/util/CLICommandCacheAdmin.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/cli/util/CLICommandCacheAdmin.java
new file mode 100644
index 0000000..e9bf182
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/cli/util/CLICommandCacheAdmin.java
@@ -0,0 +1,21 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.cli.util;
+
+public class CLICommandCacheAdmin implements CLICommandTypes {
+}
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/cli/util/CacheAdminCmdExecutor.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/cli/util/CacheAdminCmdExecutor.java
new file mode 100644
index 0000000..922020f
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/cli/util/CacheAdminCmdExecutor.java
@@ -0,0 +1,37 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.cli.util;
+
+import org.apache.hadoop.hdfs.tools.CacheAdmin;
+import org.apache.hadoop.util.ToolRunner;
+
+public class CacheAdminCmdExecutor extends CommandExecutor {
+  protected String namenode = null;
+  protected CacheAdmin admin = null;
+
+  public CacheAdminCmdExecutor(String namenode, CacheAdmin admin) {
+    this.namenode = namenode;
+    this.admin = admin;
+  }
+
+  @Override
+  protected void execute(final String cmd) throws Exception {
+    String[] args = getCommandAsArgs(cmd, "NAMENODE", this.namenode);
+    ToolRunner.run(admin, args);
+  }
+}
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/DFSTestUtil.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/DFSTestUtil.java
index ce6721a..8471eb7 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/DFSTestUtil.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/DFSTestUtil.java
@@ -817,7 +817,7 @@
         DFSConfigKeys.DFS_DATANODE_HTTP_DEFAULT_PORT,
         DFSConfigKeys.DFS_DATANODE_HTTPS_DEFAULT_PORT,
         DFSConfigKeys.DFS_DATANODE_IPC_DEFAULT_PORT,
-        1, 2, 3, 4, 5, 6, "local", adminState);
+        1l, 2l, 3l, 4l, 0l, 0l, 5, 6, "local", adminState);
   }
 
   public static DatanodeDescriptor getDatanodeDescriptor(String ipAddr,
@@ -993,6 +993,20 @@
       locatedBlocks = DFSClientAdapter.callGetBlockLocations(
           cluster.getNameNodeRpc(nnIndex), filePath, 0L, bytes.length);
     } while (locatedBlocks.isUnderConstruction());
+    // OP_ADD_CACHE_POOL 35
+    filesystem.addCachePool(new CachePoolInfo("pool1"));
+    // OP_MODIFY_CACHE_POOL 36
+    filesystem.modifyCachePool(new CachePoolInfo("pool1").setWeight(99));
+    // OP_ADD_PATH_BASED_CACHE_DIRECTIVE 33
+    PathBasedCacheDescriptor pbcd = filesystem.addPathBasedCacheDirective(
+        new PathBasedCacheDirective.Builder().
+            setPath(new Path("/path")).
+            setPool("pool1").
+            build());
+    // OP_REMOVE_PATH_BASED_CACHE_DESCRIPTOR 34
+    filesystem.removePathBasedCacheDescriptor(pbcd);
+    // OP_REMOVE_CACHE_POOL 37
+    filesystem.removeCachePool("pool1");
   }
 
   public static void abortStream(DFSOutputStream out) throws IOException {
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/LogVerificationAppender.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/LogVerificationAppender.java
index d6698b8..10ef47b 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/LogVerificationAppender.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/LogVerificationAppender.java
@@ -61,4 +61,15 @@
     }
     return count;
   }
+
+  public int countLinesWithMessage(final String text) {
+    int count = 0;
+    for (LoggingEvent e: getLog()) {
+      String msg = e.getRenderedMessage();
+      if (msg != null && msg.contains(text)) {
+        count++;
+      }
+    }
+    return count;
+  }
 }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestDatanodeConfig.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestDatanodeConfig.java
index 6256517..8e9d013 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestDatanodeConfig.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestDatanodeConfig.java
@@ -20,6 +20,7 @@
 import static org.apache.hadoop.hdfs.server.common.Util.fileAsURI;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assume.assumeTrue;
 
 import java.io.File;
 import java.io.IOException;
@@ -30,6 +31,8 @@
 import org.apache.hadoop.fs.FileUtil;
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.StartupOption;
 import org.apache.hadoop.hdfs.server.datanode.DataNode;
+import org.apache.hadoop.io.nativeio.NativeIO;
+import org.apache.hadoop.test.GenericTestUtils;
 import org.junit.AfterClass;
 import org.junit.BeforeClass;
 import org.junit.Test;
@@ -106,4 +109,38 @@
       throw new IOException("Bad URI", e);
     }
   }
+
+  @Test(timeout=60000)
+  public void testMemlockLimit() throws Exception {
+    assumeTrue(NativeIO.isAvailable());
+    final long memlockLimit = NativeIO.getMemlockLimit();
+
+    // Can't increase the memlock limit past the maximum.
+    assumeTrue(memlockLimit != Long.MAX_VALUE);
+
+    Configuration conf = cluster.getConfiguration(0);
+    long prevLimit = conf.
+        getLong(DFSConfigKeys.DFS_DATANODE_MAX_LOCKED_MEMORY_KEY,
+            DFSConfigKeys.DFS_DATANODE_MAX_LOCKED_MEMORY_DEFAULT);
+    try {
+      // Try starting the DN with limit configured to the ulimit
+      conf.setLong(DFSConfigKeys.DFS_DATANODE_MAX_LOCKED_MEMORY_KEY,
+          memlockLimit);
+      DataNode dn = null;
+      dn = DataNode.createDataNode(new String[]{},  conf);
+      dn.shutdown();
+      // Try starting the DN with a limit > ulimit
+      conf.setLong(DFSConfigKeys.DFS_DATANODE_MAX_LOCKED_MEMORY_KEY,
+          memlockLimit+1);
+      try {
+        dn = DataNode.createDataNode(new String[]{}, conf);
+      } catch (RuntimeException e) {
+        GenericTestUtils.assertExceptionContains(
+            "more than the datanode's available RLIMIT_MEMLOCK", e);
+      }
+    } finally {
+      conf.setLong(DFSConfigKeys.DFS_DATANODE_MAX_LOCKED_MEMORY_KEY,
+          prevLimit);
+    }
+  }
 }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/protocolPB/TestClientNamenodeProtocolServerSideTranslatorPB.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/protocolPB/TestClientNamenodeProtocolServerSideTranslatorPB.java
new file mode 100644
index 0000000..cfc09c7
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/protocolPB/TestClientNamenodeProtocolServerSideTranslatorPB.java
@@ -0,0 +1,57 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.protocolPB;
+
+import static org.junit.Assert.*;
+import static org.mockito.Mockito.*;
+
+import org.junit.Test;
+
+import org.apache.hadoop.hdfs.protocol.AddPathBasedCacheDirectiveException.EmptyPathError;
+import org.apache.hadoop.hdfs.protocol.ClientProtocol;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.AddPathBasedCacheDirectiveRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.PathBasedCacheDirectiveProto;
+
+import com.google.protobuf.RpcController;
+import com.google.protobuf.ServiceException;
+
+public class TestClientNamenodeProtocolServerSideTranslatorPB {
+
+  @Test
+  public void testAddPathBasedCacheDirectiveEmptyPathError() throws Exception {
+    ClientProtocol server = mock(ClientProtocol.class);
+    RpcController controller = mock(RpcController.class);
+    AddPathBasedCacheDirectiveRequestProto request = 
+        AddPathBasedCacheDirectiveRequestProto.newBuilder().
+            setDirective(PathBasedCacheDirectiveProto.newBuilder().
+                setPath("").
+                setPool("pool").
+                setReplication(1).
+                build()).
+            build();
+    ClientNamenodeProtocolServerSideTranslatorPB translator =
+        new ClientNamenodeProtocolServerSideTranslatorPB(server);
+    try {
+      translator.addPathBasedCacheDirective(controller, request);
+      fail("Expected ServiceException");
+    } catch (ServiceException e) {
+      assertNotNull(e.getCause());
+      assertTrue(e.getCause() instanceof EmptyPathError);
+    }
+  }
+}
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestBlockManager.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestBlockManager.java
index e88ec92..89a46ef 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestBlockManager.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestBlockManager.java
@@ -98,7 +98,9 @@
       cluster.add(dn);
       dn.updateHeartbeat(
           2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L,
-          2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 0, 0);
+          2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L,
+          0L, 0L,
+          0, 0);
       bm.getDatanodeManager().checkIfClusterIsNowMultiRack(dn);
     }
   }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestCachedBlocksList.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestCachedBlocksList.java
new file mode 100644
index 0000000..0643346
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestCachedBlocksList.java
@@ -0,0 +1,151 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.server.blockmanagement;
+
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.Random;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.hdfs.protocol.DatanodeID;
+import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor;
+import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor.CachedBlocksList;
+import org.apache.hadoop.hdfs.server.namenode.CachedBlock;
+import org.junit.Assert;
+import org.junit.Test;
+
+public class TestCachedBlocksList {
+  public static final Log LOG = LogFactory.getLog(TestCachedBlocksList.class);
+
+  @Test(timeout=60000)
+  public void testSingleList() {
+    DatanodeDescriptor dn = new DatanodeDescriptor(
+      new DatanodeID("127.0.0.1", "localhost", "abcd", 5000, 5001, 5002, 5003));
+    CachedBlock[] blocks = new CachedBlock[] {
+          new CachedBlock(0L, (short)1, true),
+          new CachedBlock(1L, (short)1, true),
+          new CachedBlock(2L, (short)1, true),
+      };
+    // check that lists are empty
+    Assert.assertTrue("expected pending cached list to start off empty.", 
+        !dn.getPendingCached().iterator().hasNext());
+    Assert.assertTrue("expected cached list to start off empty.", 
+        !dn.getCached().iterator().hasNext());
+    Assert.assertTrue("expected pending uncached list to start off empty.", 
+        !dn.getPendingUncached().iterator().hasNext());
+    // add a block to the back
+    Assert.assertTrue(dn.getCached().add(blocks[0]));
+    Assert.assertTrue("expected pending cached list to still be empty.", 
+        !dn.getPendingCached().iterator().hasNext());
+    Assert.assertEquals("failed to insert blocks[0]", blocks[0],
+        dn.getCached().iterator().next());
+    Assert.assertTrue("expected pending uncached list to still be empty.", 
+        !dn.getPendingUncached().iterator().hasNext());
+    // add another block to the back
+    Assert.assertTrue(dn.getCached().add(blocks[1]));
+    Iterator<CachedBlock> iter = dn.getCached().iterator();
+    Assert.assertEquals(blocks[0], iter.next());
+    Assert.assertEquals(blocks[1], iter.next());
+    Assert.assertTrue(!iter.hasNext());
+    // add a block to the front
+    Assert.assertTrue(dn.getCached().addFirst(blocks[2]));
+    iter = dn.getCached().iterator();
+    Assert.assertEquals(blocks[2], iter.next());
+    Assert.assertEquals(blocks[0], iter.next());
+    Assert.assertEquals(blocks[1], iter.next());
+    Assert.assertTrue(!iter.hasNext());
+    // remove a block from the middle
+    Assert.assertTrue(dn.getCached().remove(blocks[0]));
+    iter = dn.getCached().iterator();
+    Assert.assertEquals(blocks[2], iter.next());
+    Assert.assertEquals(blocks[1], iter.next());
+    Assert.assertTrue(!iter.hasNext());
+    // remove all blocks
+    dn.getCached().clear();
+    Assert.assertTrue("expected cached list to be empty after clear.", 
+        !dn.getPendingCached().iterator().hasNext());
+  }
+
+  private void testAddElementsToList(CachedBlocksList list,
+      CachedBlock[] blocks) {
+    Assert.assertTrue("expected list to start off empty.", 
+        !list.iterator().hasNext());
+    for (CachedBlock block : blocks) {
+      Assert.assertTrue(list.add(block));
+    }
+  }
+
+  private void testRemoveElementsFromList(Random r,
+      CachedBlocksList list, CachedBlock[] blocks) {
+    int i = 0;
+    for (Iterator<CachedBlock> iter = list.iterator(); iter.hasNext(); ) {
+      Assert.assertEquals(blocks[i], iter.next());
+      i++;
+    }
+    if (r.nextBoolean()) {
+      LOG.info("Removing via iterator");
+      for (Iterator<CachedBlock> iter = list.iterator(); iter.hasNext() ;) {
+        iter.next();
+        iter.remove();
+      }
+    } else {
+      LOG.info("Removing in pseudo-random order");
+      CachedBlock[] remainingBlocks = Arrays.copyOf(blocks, blocks.length);
+      for (int removed = 0; removed < remainingBlocks.length; ) {
+        int toRemove = r.nextInt(remainingBlocks.length);
+        if (remainingBlocks[toRemove] != null) {
+          Assert.assertTrue(list.remove(remainingBlocks[toRemove]));
+          remainingBlocks[toRemove] = null;
+          removed++;
+        }
+      }
+    }
+    Assert.assertTrue("expected list to be empty after everything " +
+        "was removed.", !list.iterator().hasNext());
+  }
+
+  @Test(timeout=60000)
+  public void testMultipleLists() {
+    DatanodeDescriptor[] datanodes = new DatanodeDescriptor[] {
+      new DatanodeDescriptor(
+        new DatanodeID("127.0.0.1", "localhost", "abcd", 5000, 5001, 5002, 5003)),
+      new DatanodeDescriptor(
+        new DatanodeID("127.0.1.1", "localhost", "efgh", 6000, 6001, 6002, 6003)),
+    };
+    CachedBlocksList[] lists = new CachedBlocksList[] {
+        datanodes[0].getPendingCached(),
+        datanodes[0].getCached(),
+        datanodes[1].getPendingCached(),
+        datanodes[1].getCached(),
+        datanodes[1].getPendingUncached(),
+    };
+    final int NUM_BLOCKS = 8000;
+    CachedBlock[] blocks = new CachedBlock[NUM_BLOCKS];
+    for (int i = 0; i < NUM_BLOCKS; i++) {
+      blocks[i] = new CachedBlock(i, (short)i, true);
+    }
+    Random r = new Random(654);
+    for (CachedBlocksList list : lists) {
+      testAddElementsToList(list, blocks);
+    }
+    for (CachedBlocksList list : lists) {
+      testRemoveElementsFromList(r, list, blocks);
+    }
+  }
+}
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestOverReplicatedBlocks.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestOverReplicatedBlocks.java
index 972a785..38b6763 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestOverReplicatedBlocks.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestOverReplicatedBlocks.java
@@ -103,7 +103,7 @@
           String corruptMachineName = corruptDataNode.getXferAddr();
           for (DatanodeDescriptor datanode : hm.getDatanodes()) {
             if (!corruptMachineName.equals(datanode.getXferAddr())) {
-              datanode.updateHeartbeat(100L, 100L, 0L, 100L, 0, 0);
+              datanode.updateHeartbeat(100L, 100L, 0L, 100L, 0L, 0L, 0, 0);
             }
           }
 
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestReplicationPolicy.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestReplicationPolicy.java
index dfd7149..01e0111 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestReplicationPolicy.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestReplicationPolicy.java
@@ -118,7 +118,7 @@
     for (int i=0; i < NUM_OF_DATANODES; i++) {
       dataNodes[i].updateHeartbeat(
           2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L,
-          2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 0, 0);
+          2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 0L, 0L, 0, 0);
     }    
   }
 
@@ -135,7 +135,8 @@
   public void testChooseTarget1() throws Exception {
     dataNodes[0].updateHeartbeat(
         2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 
-        HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 4, 0); // overloaded
+        HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L,
+        0L, 0L, 4, 0); // overloaded
 
     DatanodeDescriptor[] targets;
     targets = chooseTarget(0);
@@ -165,7 +166,7 @@
     
     dataNodes[0].updateHeartbeat(
         2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L,
-        HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 0, 0); 
+        HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 0L, 0L, 0, 0);
   }
 
   private static DatanodeDescriptor[] chooseTarget(int numOfReplicas) {
@@ -285,7 +286,8 @@
     // make data node 0 to be not qualified to choose
     dataNodes[0].updateHeartbeat(
         2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L,
-        (HdfsConstants.MIN_BLOCKS_FOR_WRITE-1)*BLOCK_SIZE, 0L, 0, 0); // no space
+        (HdfsConstants.MIN_BLOCKS_FOR_WRITE-1)*BLOCK_SIZE, 0L,
+        0L, 0L, 0, 0); // no space
         
     DatanodeDescriptor[] targets;
     targets = chooseTarget(0);
@@ -318,7 +320,7 @@
 
     dataNodes[0].updateHeartbeat(
         2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L,
-        HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 0, 0); 
+        HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 0L, 0L, 0, 0);
   }
   
   /**
@@ -335,7 +337,7 @@
     for(int i=0; i<2; i++) {
       dataNodes[i].updateHeartbeat(
           2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L,
-          (HdfsConstants.MIN_BLOCKS_FOR_WRITE-1)*BLOCK_SIZE, 0L, 0, 0);
+          (HdfsConstants.MIN_BLOCKS_FOR_WRITE-1)*BLOCK_SIZE, 0L, 0L, 0L, 0, 0);
     }
       
     DatanodeDescriptor[] targets;
@@ -363,7 +365,7 @@
     for(int i=0; i<2; i++) {
       dataNodes[i].updateHeartbeat(
           2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L,
-          HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 0, 0);
+          HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 0L, 0L, 0, 0);
     }
   }
 
@@ -425,7 +427,7 @@
     for(int i=0; i<2; i++) {
       dataNodes[i].updateHeartbeat(
           2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L,
-          (HdfsConstants.MIN_BLOCKS_FOR_WRITE-1)*BLOCK_SIZE, 0L, 0, 0);
+          (HdfsConstants.MIN_BLOCKS_FOR_WRITE-1)*BLOCK_SIZE, 0L, 0L, 0L, 0, 0);
     }
     
     final LogVerificationAppender appender = new LogVerificationAppender();
@@ -450,7 +452,7 @@
     for(int i=0; i<2; i++) {
       dataNodes[i].updateHeartbeat(
           2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L,
-          HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 0, 0);
+          HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 0L, 0L, 0, 0);
     }
   }
 
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestReplicationPolicyWithNodeGroup.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestReplicationPolicyWithNodeGroup.java
index 5670c20..7824ba1 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestReplicationPolicyWithNodeGroup.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestReplicationPolicyWithNodeGroup.java
@@ -133,7 +133,7 @@
     for(int i=0; i<NUM_OF_DATANODES; i++) {
       dataNodes[i].updateHeartbeat(
           2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L,
-          2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 0, 0);
+          2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 0L, 0L, 0, 0);
     }
   }
   
@@ -199,7 +199,8 @@
   public void testChooseTarget1() throws Exception {
     dataNodes[0].updateHeartbeat(
         2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 
-        HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 4, 0); // overloaded
+        HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L,
+        0L, 0L, 4, 0); // overloaded
 
     DatanodeDescriptor[] targets;
     targets = chooseTarget(0);
@@ -232,7 +233,7 @@
 
     dataNodes[0].updateHeartbeat(
         2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L,
-        HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 0, 0); 
+        HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 0L, 0L, 0, 0);
   }
 
   private void verifyNoTwoTargetsOnSameNodeGroup(DatanodeDescriptor[] targets) {
@@ -299,7 +300,8 @@
     // make data node 0 to be not qualified to choose
     dataNodes[0].updateHeartbeat(
         2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L,
-        (HdfsConstants.MIN_BLOCKS_FOR_WRITE-1)*BLOCK_SIZE, 0L, 0, 0); // no space
+        (HdfsConstants.MIN_BLOCKS_FOR_WRITE-1)*BLOCK_SIZE, 0L,
+        0L, 0L, 0, 0); // no space
 
     DatanodeDescriptor[] targets;
     targets = chooseTarget(0);
@@ -330,7 +332,7 @@
 
     dataNodes[0].updateHeartbeat(
         2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L,
-        HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 0, 0); 
+        HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 0L, 0L, 0, 0);
   }
 
   /**
@@ -348,7 +350,7 @@
     for(int i=0; i<3; i++) {
       dataNodes[i].updateHeartbeat(
           2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L,
-          (HdfsConstants.MIN_BLOCKS_FOR_WRITE-1)*BLOCK_SIZE, 0L, 0, 0);
+          (HdfsConstants.MIN_BLOCKS_FOR_WRITE-1)*BLOCK_SIZE, 0L, 0L, 0L, 0, 0);
     }
 
     DatanodeDescriptor[] targets;
@@ -576,11 +578,11 @@
     for(int i=0; i<NUM_OF_DATANODES_BOUNDARY; i++) {
         dataNodes[0].updateHeartbeat(
                 2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L,
-                (HdfsConstants.MIN_BLOCKS_FOR_WRITE-1)*BLOCK_SIZE, 0L, 0, 0);
+                (HdfsConstants.MIN_BLOCKS_FOR_WRITE-1)*BLOCK_SIZE, 0L, 0L, 0L, 0, 0);
         
       dataNodesInBoundaryCase[i].updateHeartbeat(
           2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L,
-          2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 0, 0);
+          2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 0L, 0L, 0, 0);
     }
 
     DatanodeDescriptor[] targets;
@@ -611,7 +613,7 @@
     for(int i=0; i<NUM_OF_DATANODES_BOUNDARY; i++) {
       dataNodesInBoundaryCase[i].updateHeartbeat(
           2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L,
-          2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 0, 0);
+          2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 0L, 0L, 0, 0);
     }
     List<DatanodeDescriptor> chosenNodes = new ArrayList<DatanodeDescriptor>();
     chosenNodes.add(dataNodesInBoundaryCase[0]);
@@ -651,7 +653,7 @@
     for(int i=0; i<NUM_OF_DATANODES_MORE_TARGETS; i++) {
       dataNodesInMoreTargetsCase[i].updateHeartbeat(
           2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L,
-          2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 0, 0);
+          2*HdfsConstants.MIN_BLOCKS_FOR_WRITE*BLOCK_SIZE, 0L, 0L, 0L, 0, 0);
     }
 
     DatanodeDescriptor[] targets;
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/common/TestJspHelper.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/common/TestJspHelper.java
index 3c3485d..075eb07 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/common/TestJspHelper.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/common/TestJspHelper.java
@@ -452,9 +452,9 @@
     DatanodeID dnId2 = new DatanodeID("127.0.0.2", "localhost2", "storage2",
         1235, 2346, 3457, 4568);
     DatanodeDescriptor dnDesc1 = new DatanodeDescriptor(dnId1, "rack1", 1024,
-        100, 924, 100, 10, 2);
+        100, 924, 100, 5l, 3l, 10, 2);
     DatanodeDescriptor dnDesc2 = new DatanodeDescriptor(dnId2, "rack2", 2500,
-        200, 1848, 200, 20, 1);
+        200, 1848, 200, 10l, 2l, 20, 1);
     ArrayList<DatanodeDescriptor> live = new ArrayList<DatanodeDescriptor>();
     live.add(dnDesc1);
     live.add(dnDesc2);
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/SimulatedFSDataset.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/SimulatedFSDataset.java
index 274e5a3..d5df755 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/SimulatedFSDataset.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/SimulatedFSDataset.java
@@ -24,6 +24,7 @@
 import java.io.OutputStream;
 import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 import java.util.Random;
@@ -465,6 +466,11 @@
     return new BlockListAsLongs(blocks, null);
   }
 
+  @Override // FsDatasetSpi
+  public List<Long> getCacheReport(String bpid) {
+    return new LinkedList<Long>();
+  }
+
   @Override // FSDatasetMBean
   public long getCapacity() {
     return storage.getCapacity();
@@ -490,6 +496,16 @@
     return storage.getNumFailedVolumes();
   }
 
+  @Override // FSDatasetMBean
+  public long getDnCacheUsed() {
+    return 0l;
+  }
+
+  @Override // FSDatasetMBean
+  public long getDnCacheCapacity() {
+    return 0l;
+  }
+
   @Override // FsDatasetSpi
   public synchronized long getLength(ExtendedBlock b) throws IOException {
     final Map<Block, BInfo> map = getMap(b.getBlockPoolId());
@@ -559,6 +575,18 @@
     }
   }
 
+  @Override // FSDatasetSpi
+  public void cache(String bpid, long[] cacheBlks) {
+    throw new UnsupportedOperationException(
+        "SimulatedFSDataset does not support cache operation!");
+  }
+
+  @Override // FSDatasetSpi
+  public void uncache(String bpid, long[] uncacheBlks) {
+    throw new UnsupportedOperationException(
+        "SimulatedFSDataset does not support uncache operation!");
+  }
+
   private BInfo getBInfo(final ExtendedBlock b) {
     final Map<Block, BInfo> map = blockMap.get(b.getBlockPoolId());
     return map == null? null: map.get(b.getLocalBlock());
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestBPOfferService.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestBPOfferService.java
index 8eb226b..420dfca 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestBPOfferService.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestBPOfferService.java
@@ -126,6 +126,8 @@
       .when(mock).sendHeartbeat(
           Mockito.any(DatanodeRegistration.class),
           Mockito.any(StorageReport[].class),
+          Mockito.anyLong(),
+          Mockito.anyLong(),
           Mockito.anyInt(),
           Mockito.anyInt(),
           Mockito.anyInt());
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestBlockRecovery.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestBlockRecovery.java
index a5792ad..bc78744 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestBlockRecovery.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestBlockRecovery.java
@@ -154,6 +154,8 @@
     when(namenode.sendHeartbeat(
             Mockito.any(DatanodeRegistration.class),
             Mockito.any(StorageReport[].class),
+            Mockito.anyLong(),
+            Mockito.anyLong(),
             Mockito.anyInt(),
             Mockito.anyInt(),
             Mockito.anyInt()))
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestFsDatasetCache.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestFsDatasetCache.java
new file mode 100644
index 0000000..e6e87b9
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestFsDatasetCache.java
@@ -0,0 +1,269 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.server.datanode;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assume.assumeTrue;
+import static org.mockito.Matchers.any;
+import static org.mockito.Matchers.anyLong;
+import static org.mockito.Matchers.anyInt;
+import static org.mockito.Mockito.doReturn;
+
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.nio.channels.FileChannel;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.HdfsBlockLocation;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.ha.HAServiceProtocol.HAServiceState;
+import org.apache.hadoop.hdfs.DFSConfigKeys;
+import org.apache.hadoop.hdfs.DFSTestUtil;
+import org.apache.hadoop.hdfs.HdfsConfiguration;
+import org.apache.hadoop.hdfs.LogVerificationAppender;
+import org.apache.hadoop.hdfs.MiniDFSCluster;
+import org.apache.hadoop.hdfs.protocol.Block;
+import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
+import org.apache.hadoop.hdfs.protocolPB.DatanodeProtocolClientSideTranslatorPB;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsDatasetSpi;
+import org.apache.hadoop.hdfs.server.namenode.FSImage;
+import org.apache.hadoop.hdfs.server.namenode.NameNode;
+import org.apache.hadoop.hdfs.server.protocol.BlockIdCommand;
+import org.apache.hadoop.hdfs.server.protocol.DatanodeCommand;
+import org.apache.hadoop.hdfs.server.protocol.DatanodeProtocol;
+import org.apache.hadoop.hdfs.server.protocol.DatanodeRegistration;
+import org.apache.hadoop.hdfs.server.protocol.HeartbeatResponse;
+import org.apache.hadoop.hdfs.server.protocol.NNHAStatusHeartbeat;
+import org.apache.hadoop.hdfs.server.protocol.StorageReport;
+import org.apache.hadoop.io.nativeio.NativeIO;
+import org.apache.log4j.Logger;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+public class TestFsDatasetCache {
+
+  // Most Linux installs allow a default of 64KB locked memory
+  private static final long CACHE_CAPACITY = 64 * 1024;
+  private static final long BLOCK_SIZE = 4096;
+
+  private static Configuration conf;
+  private static MiniDFSCluster cluster = null;
+  private static FileSystem fs;
+  private static NameNode nn;
+  private static FSImage fsImage;
+  private static DataNode dn;
+  private static FsDatasetSpi<?> fsd;
+  private static DatanodeProtocolClientSideTranslatorPB spyNN;
+
+  @Before
+  public void setUp() throws Exception {
+    assumeTrue(!Path.WINDOWS);
+    assumeTrue(NativeIO.isAvailable());
+    conf = new HdfsConfiguration();
+    conf.setLong(DFSConfigKeys.DFS_BLOCK_SIZE_KEY, BLOCK_SIZE);
+    conf.setLong(DFSConfigKeys.DFS_DATANODE_MAX_LOCKED_MEMORY_KEY,
+        CACHE_CAPACITY);
+    conf.setLong(DFSConfigKeys.DFS_HEARTBEAT_INTERVAL_KEY, 1);
+
+    cluster = new MiniDFSCluster.Builder(conf)
+        .numDataNodes(1).build();
+    cluster.waitActive();
+
+    fs = cluster.getFileSystem();
+    nn = cluster.getNameNode();
+    fsImage = nn.getFSImage();
+    dn = cluster.getDataNodes().get(0);
+    fsd = dn.getFSDataset();
+
+    spyNN = DataNodeTestUtils.spyOnBposToNN(dn, nn);
+  }
+
+  @After
+  public void tearDown() throws Exception {
+    if (fs != null) {
+      fs.close();
+    }
+    if (cluster != null) {
+      cluster.shutdown();
+    }
+  }
+
+  private static void setHeartbeatResponse(DatanodeCommand[] cmds)
+      throws IOException {
+    HeartbeatResponse response = new HeartbeatResponse(
+        cmds,
+        new NNHAStatusHeartbeat(HAServiceState.ACTIVE,
+        fsImage.getLastAppliedOrWrittenTxId()));
+    doReturn(response).when(spyNN).sendHeartbeat(
+        (DatanodeRegistration) any(),
+        (StorageReport[]) any(), anyLong(), anyLong(),
+        anyInt(), anyInt(), anyInt());
+  }
+
+  private static DatanodeCommand[] cacheBlock(HdfsBlockLocation loc) {
+    return cacheBlocks(new HdfsBlockLocation[] {loc});
+  }
+
+  private static DatanodeCommand[] cacheBlocks(HdfsBlockLocation[] locs) {
+    return new DatanodeCommand[] {
+        getResponse(locs, DatanodeProtocol.DNA_CACHE)
+    };
+  }
+
+  private static DatanodeCommand[] uncacheBlock(HdfsBlockLocation loc) {
+    return uncacheBlocks(new HdfsBlockLocation[] {loc});
+  }
+
+  private static DatanodeCommand[] uncacheBlocks(HdfsBlockLocation[] locs) {
+    return new DatanodeCommand[] {
+        getResponse(locs, DatanodeProtocol.DNA_UNCACHE)
+    };
+  }
+
+  /**
+   * Creates a cache or uncache DatanodeCommand from an array of locations
+   */
+  private static DatanodeCommand getResponse(HdfsBlockLocation[] locs,
+      int action) {
+    String bpid = locs[0].getLocatedBlock().getBlock().getBlockPoolId();
+    long[] blocks = new long[locs.length];
+    for (int i=0; i<locs.length; i++) {
+      blocks[i] = locs[i].getLocatedBlock().getBlock().getBlockId();
+    }
+    return new BlockIdCommand(action, bpid, blocks);
+  }
+
+  private static long[] getBlockSizes(HdfsBlockLocation[] locs)
+      throws Exception {
+    long[] sizes = new long[locs.length];
+    for (int i=0; i<locs.length; i++) {
+      HdfsBlockLocation loc = locs[i];
+      String bpid = loc.getLocatedBlock().getBlock().getBlockPoolId();
+      Block block = loc.getLocatedBlock().getBlock().getLocalBlock();
+      ExtendedBlock extBlock = new ExtendedBlock(bpid, block);
+      FileChannel blockChannel =
+          ((FileInputStream)fsd.getBlockInputStream(extBlock, 0)).getChannel();
+      sizes[i] = blockChannel.size();
+    }
+    return sizes;
+  }
+
+  /**
+   * Blocks until cache usage hits the expected new value.
+   */
+  private long verifyExpectedCacheUsage(final long expected) throws Exception {
+    long cacheUsed = fsd.getDnCacheUsed();
+    while (cacheUsed != expected) {
+      cacheUsed = fsd.getDnCacheUsed();
+      Thread.sleep(100);
+    }
+    assertEquals("Unexpected amount of cache used", expected, cacheUsed);
+    return cacheUsed;
+  }
+
+  @Test(timeout=60000)
+  public void testCacheAndUncacheBlock() throws Exception {
+    final int NUM_BLOCKS = 5;
+
+    // Write a test file
+    final Path testFile = new Path("/testCacheBlock");
+    final long testFileLen = BLOCK_SIZE*NUM_BLOCKS;
+    DFSTestUtil.createFile(fs, testFile, testFileLen, (short)1, 0xABBAl);
+
+    // Get the details of the written file
+    HdfsBlockLocation[] locs =
+        (HdfsBlockLocation[])fs.getFileBlockLocations(testFile, 0, testFileLen);
+    assertEquals("Unexpected number of blocks", NUM_BLOCKS, locs.length);
+    final long[] blockSizes = getBlockSizes(locs);
+
+    // Check initial state
+    final long cacheCapacity = fsd.getDnCacheCapacity();
+    long cacheUsed = fsd.getDnCacheUsed();
+    long current = 0;
+    assertEquals("Unexpected cache capacity", CACHE_CAPACITY, cacheCapacity);
+    assertEquals("Unexpected amount of cache used", current, cacheUsed);
+
+    // Cache each block in succession, checking each time
+    for (int i=0; i<NUM_BLOCKS; i++) {
+      setHeartbeatResponse(cacheBlock(locs[i]));
+      current = verifyExpectedCacheUsage(current + blockSizes[i]);
+    }
+
+    // Uncache each block in succession, again checking each time
+    for (int i=0; i<NUM_BLOCKS; i++) {
+      setHeartbeatResponse(uncacheBlock(locs[i]));
+      current = verifyExpectedCacheUsage(current - blockSizes[i]);
+    }
+  }
+
+  @Test(timeout=60000)
+  public void testFilesExceedMaxLockedMemory() throws Exception {
+    // Create some test files that will exceed total cache capacity
+    // Don't forget that meta files take up space too!
+    final int numFiles = 4;
+    final long fileSize = CACHE_CAPACITY / numFiles;
+    final Path[] testFiles = new Path[4];
+    final HdfsBlockLocation[][] fileLocs = new HdfsBlockLocation[numFiles][];
+    final long[] fileSizes = new long[numFiles];
+    for (int i=0; i<numFiles; i++) {
+      testFiles[i] = new Path("/testFilesExceedMaxLockedMemory-" + i);
+      DFSTestUtil.createFile(fs, testFiles[i], fileSize, (short)1, 0xDFAl);
+      fileLocs[i] = (HdfsBlockLocation[])fs.getFileBlockLocations(
+          testFiles[i], 0, fileSize);
+      // Get the file size (sum of blocks)
+      long[] sizes = getBlockSizes(fileLocs[i]);
+      for (int j=0; j<sizes.length; j++) {
+        fileSizes[i] += sizes[j];
+      }
+    }
+
+    // Cache the first n-1 files
+    long current = 0;
+    for (int i=0; i<numFiles-1; i++) {
+      setHeartbeatResponse(cacheBlocks(fileLocs[i]));
+      current = verifyExpectedCacheUsage(current + fileSizes[i]);
+    }
+    final long oldCurrent = current;
+
+    // nth file should hit a capacity exception
+    final LogVerificationAppender appender = new LogVerificationAppender();
+    final Logger logger = Logger.getRootLogger();
+    logger.addAppender(appender);
+    setHeartbeatResponse(cacheBlocks(fileLocs[numFiles-1]));
+    int lines = 0;
+    while (lines == 0) {
+      Thread.sleep(100);
+      lines = appender.countLinesWithMessage(
+          DFSConfigKeys.DFS_DATANODE_MAX_LOCKED_MEMORY_KEY + " exceeded");
+    }
+
+    // Uncache the cached part of the nth file
+    setHeartbeatResponse(uncacheBlocks(fileLocs[numFiles-1]));
+    while (fsd.getDnCacheUsed() != oldCurrent) {
+      Thread.sleep(100);
+    }
+
+    // Uncache the n-1 files
+    for (int i=0; i<numFiles-1; i++) {
+      setHeartbeatResponse(uncacheBlocks(fileLocs[i]));
+      current = verifyExpectedCacheUsage(current - fileSizes[i]);
+    }
+  }
+}
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/NNThroughputBenchmark.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/NNThroughputBenchmark.java
index b6882d6..55bf955 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/NNThroughputBenchmark.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/NNThroughputBenchmark.java
@@ -845,8 +845,8 @@
       // TODO:FEDERATION currently a single block pool is supported
       StorageReport[] rep = { new StorageReport(dnRegistration.getStorageID(),
           false, DF_CAPACITY, DF_USED, DF_CAPACITY - DF_USED, DF_USED) };
-      DatanodeCommand[] cmds = nameNodeProto.sendHeartbeat(dnRegistration,
-          rep, 0, 0, 0).getCommands();
+      DatanodeCommand[] cmds = nameNodeProto.sendHeartbeat(dnRegistration, rep,
+          0L, 0L, 0, 0, 0).getCommands();
       if(cmds != null) {
         for (DatanodeCommand cmd : cmds ) {
           if(LOG.isDebugEnabled()) {
@@ -893,7 +893,7 @@
       StorageReport[] rep = { new StorageReport(dnRegistration.getStorageID(),
           false, DF_CAPACITY, DF_USED, DF_CAPACITY - DF_USED, DF_USED) };
       DatanodeCommand[] cmds = nameNodeProto.sendHeartbeat(dnRegistration,
-          rep, 0, 0, 0).getCommands();
+          rep, 0L, 0L, 0, 0, 0).getCommands();
       if (cmds != null) {
         for (DatanodeCommand cmd : cmds) {
           if (cmd.getAction() == DatanodeProtocol.DNA_TRANSFER) {
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/NameNodeAdapter.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/NameNodeAdapter.java
index cf64c33..b83adec 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/NameNodeAdapter.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/NameNodeAdapter.java
@@ -111,7 +111,8 @@
   public static HeartbeatResponse sendHeartBeat(DatanodeRegistration nodeReg,
       DatanodeDescriptor dd, FSNamesystem namesystem) throws IOException {
     return namesystem.handleHeartbeat(nodeReg, dd.getCapacity(), 
-        dd.getDfsUsed(), dd.getRemaining(), dd.getBlockPoolUsed(), 0, 0, 0);
+        dd.getDfsUsed(), dd.getRemaining(), dd.getBlockPoolUsed(),
+        dd.getCacheCapacity(), dd.getCacheRemaining(), 0, 0, 0);
   }
 
   public static boolean setReplication(final FSNamesystem ns,
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/OfflineEditsViewerHelper.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/OfflineEditsViewerHelper.java
index 6fd1445..ca12bf1 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/OfflineEditsViewerHelper.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/OfflineEditsViewerHelper.java
@@ -39,8 +39,11 @@
 import org.apache.hadoop.hdfs.DFSTestUtil;
 import org.apache.hadoop.hdfs.DistributedFileSystem;
 import org.apache.hadoop.hdfs.MiniDFSCluster;
+import org.apache.hadoop.hdfs.protocol.CachePoolInfo;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants;
 import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDescriptor;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDirective;
 import org.apache.hadoop.hdfs.server.common.Storage.StorageDirectory;
 import org.apache.hadoop.hdfs.server.common.Util;
 import org.apache.hadoop.hdfs.server.namenode.NNStorage.NameNodeDirType;
@@ -229,6 +232,26 @@
     // OP_UPDATE_MASTER_KEY 21
     //   done by getDelegationTokenSecretManager().startThreads();
 
+    // OP_ADD_CACHE_POOL 35
+    final String pool = "poolparty";
+    dfs.addCachePool(new CachePoolInfo(pool));
+    // OP_MODIFY_CACHE_POOL 36
+    dfs.modifyCachePool(new CachePoolInfo(pool)
+        .setOwnerName("carlton")
+        .setGroupName("party")
+        .setMode(new FsPermission((short)0700))
+        .setWeight(1989));
+    // OP_ADD_PATH_BASED_CACHE_DIRECTIVE 33
+    PathBasedCacheDescriptor descriptor =
+        dfs.addPathBasedCacheDirective(new PathBasedCacheDirective.Builder().
+            setPath(new Path("/bar")).
+            setReplication((short)1).
+            setPool(pool).
+            build());
+    // OP_REMOVE_PATH_BASED_CACHE_DESCRIPTOR 34
+    dfs.removePathBasedCacheDescriptor(descriptor);
+    // OP_REMOVE_CACHE_POOL 37
+    dfs.removeCachePool(pool);
     // sync to disk, otherwise we parse partial edits
     cluster.getNameNode().getFSImage().getEditLog().logSync();
     
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestDeadDatanode.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestDeadDatanode.java
index d78198a..6eed13e 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestDeadDatanode.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestDeadDatanode.java
@@ -142,7 +142,8 @@
     // that asks datanode to register again
     StorageReport[] rep = { new StorageReport(reg.getStorageID(), false, 0, 0,
         0, 0) };
-    DatanodeCommand[] cmd = dnp.sendHeartbeat(reg, rep, 0, 0, 0).getCommands();
+    DatanodeCommand[] cmd = dnp.sendHeartbeat(reg, rep, 0L, 0L, 0, 0, 0)
+        .getCommands();
     assertEquals(1, cmd.length);
     assertEquals(cmd[0].getAction(), RegisterCommand.REGISTER
         .getAction());
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestNamenodeRetryCache.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestNamenodeRetryCache.java
index ddb7c0f..576c3ea 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestNamenodeRetryCache.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestNamenodeRetryCache.java
@@ -413,7 +413,7 @@
     
     LightWeightCache<CacheEntry, CacheEntry> cacheSet = 
         (LightWeightCache<CacheEntry, CacheEntry>) namesystem.getRetryCache().getCacheSet();
-    assertEquals(14, cacheSet.size());
+    assertEquals(19, cacheSet.size());
     
     Map<CacheEntry, CacheEntry> oldEntries = 
         new HashMap<CacheEntry, CacheEntry>();
@@ -432,7 +432,7 @@
     assertTrue(namesystem.hasRetryCache());
     cacheSet = (LightWeightCache<CacheEntry, CacheEntry>) namesystem
         .getRetryCache().getCacheSet();
-    assertEquals(14, cacheSet.size());
+    assertEquals(19, cacheSet.size());
     iter = cacheSet.iterator();
     while (iter.hasNext()) {
       CacheEntry entry = iter.next();
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestPathBasedCacheRequests.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestPathBasedCacheRequests.java
new file mode 100644
index 0000000..dce0b17
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestPathBasedCacheRequests.java
@@ -0,0 +1,743 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.server.namenode;
+
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_DATANODE_MAX_LOCKED_MEMORY_KEY;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_HEARTBEAT_INTERVAL_KEY;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_BLOCK_SIZE_KEY;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_CACHING_ENABLED_KEY;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_CACHEREPORT_INTERVAL_MSEC_KEY;
+import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_PATH_BASED_CACHE_REFRESH_INTERVAL_MS;
+import static junit.framework.Assert.assertTrue;
+import static junit.framework.Assert.fail;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+
+import java.io.IOException;
+import java.security.PrivilegedExceptionAction;
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.LinkedList;
+import java.util.List;
+
+import junit.framework.Assert;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.FileSystemTestHelper;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.fs.RemoteIterator;
+import org.apache.hadoop.fs.permission.FsPermission;
+import org.apache.hadoop.hdfs.DFSConfigKeys;
+import org.apache.hadoop.hdfs.DistributedFileSystem;
+import org.apache.hadoop.hdfs.HdfsConfiguration;
+import org.apache.hadoop.hdfs.MiniDFSCluster;
+import org.apache.hadoop.hdfs.protocol.AddPathBasedCacheDirectiveException.InvalidPathNameError;
+import org.apache.hadoop.hdfs.protocol.AddPathBasedCacheDirectiveException.InvalidPoolNameError;
+import org.apache.hadoop.hdfs.protocol.AddPathBasedCacheDirectiveException.PoolWritePermissionDeniedError;
+import org.apache.hadoop.hdfs.protocol.CachePoolInfo;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDescriptor;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDirective;
+import org.apache.hadoop.hdfs.protocol.RemovePathBasedCacheDescriptorException.InvalidIdException;
+import org.apache.hadoop.hdfs.protocol.RemovePathBasedCacheDescriptorException.NoSuchIdException;
+import org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor.CachedBlocksList.Type;
+import org.apache.hadoop.hdfs.server.protocol.NamenodeProtocols;
+import org.apache.hadoop.io.nativeio.NativeIO;
+import org.apache.hadoop.security.UserGroupInformation;
+import org.apache.hadoop.test.GenericTestUtils;
+import org.apache.hadoop.util.GSet;
+import org.junit.After;
+import org.junit.Assume;
+import org.junit.Before;
+import org.junit.Test;
+
+import com.google.common.base.Supplier;
+
+public class TestPathBasedCacheRequests {
+  static final Log LOG = LogFactory.getLog(TestPathBasedCacheRequests.class);
+
+  private static final UserGroupInformation unprivilegedUser =
+      UserGroupInformation.createRemoteUser("unprivilegedUser");
+
+  static private Configuration conf;
+  static private MiniDFSCluster cluster;
+  static private DistributedFileSystem dfs;
+  static private NamenodeProtocols proto;
+
+  @Before
+  public void setup() throws Exception {
+    conf = new HdfsConfiguration();
+    // set low limits here for testing purposes
+    conf.setInt(DFSConfigKeys.DFS_NAMENODE_LIST_CACHE_POOLS_NUM_RESPONSES, 2);
+    conf.setInt(DFSConfigKeys.DFS_NAMENODE_LIST_CACHE_DESCRIPTORS_NUM_RESPONSES, 2);
+    cluster = new MiniDFSCluster.Builder(conf).numDataNodes(1).build();
+    cluster.waitActive();
+    dfs = cluster.getFileSystem();
+    proto = cluster.getNameNodeRpc();
+  }
+
+  @After
+  public void teardown() throws Exception {
+    if (cluster != null) {
+      cluster.shutdown();
+    }
+  }
+
+  @Test(timeout=60000)
+  public void testBasicPoolOperations() throws Exception {
+    final String poolName = "pool1";
+    CachePoolInfo info = new CachePoolInfo(poolName).
+        setOwnerName("bob").setGroupName("bobgroup").
+        setMode(new FsPermission((short)0755)).setWeight(150);
+
+    // Add a pool
+    dfs.addCachePool(info);
+
+    // Do some bad addCachePools
+    try {
+      dfs.addCachePool(info);
+      fail("added the pool with the same name twice");
+    } catch (IOException ioe) {
+      GenericTestUtils.assertExceptionContains("pool1 already exists", ioe);
+    }
+    try {
+      dfs.addCachePool(new CachePoolInfo(""));
+      fail("added empty pool");
+    } catch (IOException ioe) {
+      GenericTestUtils.assertExceptionContains("invalid empty cache pool name",
+          ioe);
+    }
+    try {
+      dfs.addCachePool(null);
+      fail("added null pool");
+    } catch (IOException ioe) {
+      GenericTestUtils.assertExceptionContains("CachePoolInfo is null", ioe);
+    }
+    try {
+      proto.addCachePool(new CachePoolInfo(""));
+      fail("added empty pool");
+    } catch (IOException ioe) {
+      GenericTestUtils.assertExceptionContains("invalid empty cache pool name",
+          ioe);
+    }
+    try {
+      proto.addCachePool(null);
+      fail("added null pool");
+    } catch (IOException ioe) {
+      GenericTestUtils.assertExceptionContains("CachePoolInfo is null", ioe);
+    }
+
+    // Modify the pool
+    info.setOwnerName("jane").setGroupName("janegroup")
+        .setMode(new FsPermission((short)0700)).setWeight(314);
+    dfs.modifyCachePool(info);
+
+    // Do some invalid modify pools
+    try {
+      dfs.modifyCachePool(new CachePoolInfo("fool"));
+      fail("modified non-existent cache pool");
+    } catch (IOException ioe) {
+      GenericTestUtils.assertExceptionContains("fool does not exist", ioe);
+    }
+    try {
+      dfs.modifyCachePool(new CachePoolInfo(""));
+      fail("modified empty pool");
+    } catch (IOException ioe) {
+      GenericTestUtils.assertExceptionContains("invalid empty cache pool name",
+          ioe);
+    }
+    try {
+      dfs.modifyCachePool(null);
+      fail("modified null pool");
+    } catch (IOException ioe) {
+      GenericTestUtils.assertExceptionContains("CachePoolInfo is null", ioe);
+    }
+    try {
+      proto.modifyCachePool(new CachePoolInfo(""));
+      fail("modified empty pool");
+    } catch (IOException ioe) {
+      GenericTestUtils.assertExceptionContains("invalid empty cache pool name",
+          ioe);
+    }
+    try {
+      proto.modifyCachePool(null);
+      fail("modified null pool");
+    } catch (IOException ioe) {
+      GenericTestUtils.assertExceptionContains("CachePoolInfo is null", ioe);
+    }
+
+    // Remove the pool
+    dfs.removeCachePool(poolName);
+    // Do some bad removePools
+    try {
+      dfs.removeCachePool("pool99");
+      fail("expected to get an exception when " +
+          "removing a non-existent pool.");
+    } catch (IOException ioe) {
+      GenericTestUtils.assertExceptionContains("can't remove " +
+          "non-existent cache pool", ioe);
+    }
+    try {
+      dfs.removeCachePool(poolName);
+      Assert.fail("expected to get an exception when " +
+          "removing a non-existent pool.");
+    } catch (IOException ioe) {
+      GenericTestUtils.assertExceptionContains("can't remove " +
+          "non-existent cache pool", ioe);
+    }
+    try {
+      dfs.removeCachePool("");
+      fail("removed empty pool");
+    } catch (IOException ioe) {
+      GenericTestUtils.assertExceptionContains("invalid empty cache pool name",
+          ioe);
+    }
+    try {
+      dfs.removeCachePool(null);
+      fail("removed null pool");
+    } catch (IOException ioe) {
+      GenericTestUtils.assertExceptionContains("invalid empty cache pool name",
+          ioe);
+    }
+    try {
+      proto.removeCachePool("");
+      fail("removed empty pool");
+    } catch (IOException ioe) {
+      GenericTestUtils.assertExceptionContains("invalid empty cache pool name",
+          ioe);
+    }
+    try {
+      proto.removeCachePool(null);
+      fail("removed null pool");
+    } catch (IOException ioe) {
+      GenericTestUtils.assertExceptionContains("invalid empty cache pool name",
+          ioe);
+    }
+
+    info = new CachePoolInfo("pool2");
+    dfs.addCachePool(info);
+  }
+
+  @Test(timeout=60000)
+  public void testCreateAndModifyPools() throws Exception {
+    String poolName = "pool1";
+    String ownerName = "abc";
+    String groupName = "123";
+    FsPermission mode = new FsPermission((short)0755);
+    int weight = 150;
+    dfs.addCachePool(new CachePoolInfo(poolName).
+        setOwnerName(ownerName).setGroupName(groupName).
+        setMode(mode).setWeight(weight));
+    
+    RemoteIterator<CachePoolInfo> iter = dfs.listCachePools();
+    CachePoolInfo info = iter.next();
+    assertEquals(poolName, info.getPoolName());
+    assertEquals(ownerName, info.getOwnerName());
+    assertEquals(groupName, info.getGroupName());
+
+    ownerName = "def";
+    groupName = "456";
+    mode = new FsPermission((short)0700);
+    weight = 151;
+    dfs.modifyCachePool(new CachePoolInfo(poolName).
+        setOwnerName(ownerName).setGroupName(groupName).
+        setMode(mode).setWeight(weight));
+
+    iter = dfs.listCachePools();
+    info = iter.next();
+    assertEquals(poolName, info.getPoolName());
+    assertEquals(ownerName, info.getOwnerName());
+    assertEquals(groupName, info.getGroupName());
+    assertEquals(mode, info.getMode());
+    assertEquals(Integer.valueOf(weight), info.getWeight());
+
+    dfs.removeCachePool(poolName);
+    iter = dfs.listCachePools();
+    assertFalse("expected no cache pools after deleting pool", iter.hasNext());
+
+    proto.listCachePools(null);
+
+    try {
+      proto.removeCachePool("pool99");
+      Assert.fail("expected to get an exception when " +
+          "removing a non-existent pool.");
+    } catch (IOException ioe) {
+      GenericTestUtils.assertExceptionContains("can't remove non-existent",
+          ioe);
+    }
+    try {
+      proto.removeCachePool(poolName);
+      Assert.fail("expected to get an exception when " +
+          "removing a non-existent pool.");
+    } catch (IOException ioe) {
+      GenericTestUtils.assertExceptionContains("can't remove non-existent",
+          ioe);
+    }
+
+    iter = dfs.listCachePools();
+    assertFalse("expected no cache pools after deleting pool", iter.hasNext());
+  }
+
+  private static void validateListAll(
+      RemoteIterator<PathBasedCacheDescriptor> iter,
+      PathBasedCacheDescriptor... descriptors) throws Exception {
+    for (PathBasedCacheDescriptor descriptor: descriptors) {
+      assertTrue("Unexpectedly few elements", iter.hasNext());
+      assertEquals("Unexpected descriptor", descriptor, iter.next());
+    }
+    assertFalse("Unexpectedly many list elements", iter.hasNext());
+  }
+
+  private static PathBasedCacheDescriptor addAsUnprivileged(
+      final PathBasedCacheDirective directive) throws Exception {
+    return unprivilegedUser
+        .doAs(new PrivilegedExceptionAction<PathBasedCacheDescriptor>() {
+          @Override
+          public PathBasedCacheDescriptor run() throws IOException {
+            DistributedFileSystem myDfs =
+                (DistributedFileSystem) FileSystem.get(conf);
+            return myDfs.addPathBasedCacheDirective(directive);
+          }
+        });
+  }
+
+  @Test(timeout=60000)
+  public void testAddRemoveDirectives() throws Exception {
+    proto.addCachePool(new CachePoolInfo("pool1").
+        setMode(new FsPermission((short)0777)));
+    proto.addCachePool(new CachePoolInfo("pool2").
+        setMode(new FsPermission((short)0777)));
+    proto.addCachePool(new CachePoolInfo("pool3").
+        setMode(new FsPermission((short)0777)));
+    proto.addCachePool(new CachePoolInfo("pool4").
+        setMode(new FsPermission((short)0)));
+
+    PathBasedCacheDirective alpha = new PathBasedCacheDirective.Builder().
+        setPath(new Path("/alpha")).
+        setPool("pool1").
+        build();
+    PathBasedCacheDirective beta = new PathBasedCacheDirective.Builder().
+        setPath(new Path("/beta")).
+        setPool("pool2").
+        build();
+    PathBasedCacheDirective delta = new PathBasedCacheDirective.Builder().
+        setPath(new Path("/delta")).
+        setPool("pool1").
+        build();
+
+    PathBasedCacheDescriptor alphaD = addAsUnprivileged(alpha);
+    PathBasedCacheDescriptor alphaD2 = addAsUnprivileged(alpha);
+    assertFalse("Expected to get unique descriptors when re-adding an "
+        + "existing PathBasedCacheDirective",
+        alphaD.getEntryId() == alphaD2.getEntryId());
+    PathBasedCacheDescriptor betaD = addAsUnprivileged(beta);
+
+    try {
+      addAsUnprivileged(new PathBasedCacheDirective.Builder().
+          setPath(new Path("/unicorn")).
+          setPool("no_such_pool").
+          build());
+      fail("expected an error when adding to a non-existent pool.");
+    } catch (IOException ioe) {
+      assertTrue(ioe instanceof InvalidPoolNameError);
+    }
+
+    try {
+      addAsUnprivileged(new PathBasedCacheDirective.Builder().
+          setPath(new Path("/blackhole")).
+          setPool("pool4").
+          build());
+      fail("expected an error when adding to a pool with " +
+          "mode 0 (no permissions for anyone).");
+    } catch (IOException ioe) {
+      assertTrue(ioe instanceof PoolWritePermissionDeniedError);
+    }
+
+    try {
+      addAsUnprivileged(new PathBasedCacheDirective.Builder().
+          setPath(new Path("/illegal:path/")).
+          setPool("pool1").
+          build());
+      fail("expected an error when adding a malformed path " +
+          "to the cache directives.");
+    } catch (IllegalArgumentException e) {
+      // expected
+    }
+
+    try {
+      addAsUnprivileged(new PathBasedCacheDirective.Builder().
+          setPath(new Path("/emptypoolname")).
+          setReplication((short)1).
+          setPool("").
+          build());
+      Assert.fail("expected an error when adding a PathBasedCache " +
+          "directive with an empty pool name.");
+    } catch (IOException ioe) {
+      Assert.assertTrue(ioe instanceof InvalidPoolNameError);
+    }
+
+    PathBasedCacheDescriptor deltaD = addAsUnprivileged(delta);
+
+    // We expect the following to succeed, because DistributedFileSystem
+    // qualifies the path.
+    PathBasedCacheDescriptor relativeD = addAsUnprivileged(
+        new PathBasedCacheDirective.Builder().
+            setPath(new Path("relative")).
+            setPool("pool1").
+            build());
+
+    RemoteIterator<PathBasedCacheDescriptor> iter;
+    iter = dfs.listPathBasedCacheDescriptors(null, null);
+    validateListAll(iter, alphaD, alphaD2, betaD, deltaD, relativeD);
+    iter = dfs.listPathBasedCacheDescriptors("pool3", null);
+    Assert.assertFalse(iter.hasNext());
+    iter = dfs.listPathBasedCacheDescriptors("pool1", null);
+    validateListAll(iter, alphaD, alphaD2, deltaD, relativeD);
+    iter = dfs.listPathBasedCacheDescriptors("pool2", null);
+    validateListAll(iter, betaD);
+
+    dfs.removePathBasedCacheDescriptor(betaD);
+    iter = dfs.listPathBasedCacheDescriptors("pool2", null);
+    Assert.assertFalse(iter.hasNext());
+
+    try {
+      dfs.removePathBasedCacheDescriptor(betaD);
+      Assert.fail("expected an error when removing a non-existent ID");
+    } catch (IOException ioe) {
+      Assert.assertTrue(ioe instanceof NoSuchIdException);
+    }
+
+    try {
+      proto.removePathBasedCacheDescriptor(-42l);
+      Assert.fail("expected an error when removing a negative ID");
+    } catch (IOException ioe) {
+      Assert.assertTrue(ioe instanceof InvalidIdException);
+    }
+    try {
+      proto.removePathBasedCacheDescriptor(43l);
+      Assert.fail("expected an error when removing a non-existent ID");
+    } catch (IOException ioe) {
+      Assert.assertTrue(ioe instanceof NoSuchIdException);
+    }
+
+    dfs.removePathBasedCacheDescriptor(alphaD);
+    dfs.removePathBasedCacheDescriptor(alphaD2);
+    dfs.removePathBasedCacheDescriptor(deltaD);
+    dfs.removePathBasedCacheDescriptor(relativeD);
+    iter = dfs.listPathBasedCacheDescriptors(null, null);
+    assertFalse(iter.hasNext());
+  }
+
+  @Test(timeout=60000)
+  public void testCacheManagerRestart() throws Exception {
+    cluster.shutdown();
+    cluster = null;
+    HdfsConfiguration conf = createCachingConf();
+    cluster = new MiniDFSCluster.Builder(conf).numDataNodes(0).build();
+
+    cluster.waitActive();
+    DistributedFileSystem dfs = cluster.getFileSystem();
+
+    // Create and validate a pool
+    final String pool = "poolparty";
+    String groupName = "partygroup";
+    FsPermission mode = new FsPermission((short)0777);
+    int weight = 747;
+    dfs.addCachePool(new CachePoolInfo(pool)
+        .setGroupName(groupName)
+        .setMode(mode)
+        .setWeight(weight));
+    RemoteIterator<CachePoolInfo> pit = dfs.listCachePools();
+    assertTrue("No cache pools found", pit.hasNext());
+    CachePoolInfo info = pit.next();
+    assertEquals(pool, info.getPoolName());
+    assertEquals(groupName, info.getGroupName());
+    assertEquals(mode, info.getMode());
+    assertEquals(weight, (int)info.getWeight());
+    assertFalse("Unexpected # of cache pools found", pit.hasNext());
+  
+    // Create some cache entries
+    int numEntries = 10;
+    String entryPrefix = "/party-";
+    for (int i=0; i<numEntries; i++) {
+      dfs.addPathBasedCacheDirective(
+          new PathBasedCacheDirective.Builder().
+            setPath(new Path(entryPrefix + i)).setPool(pool).build());
+    }
+    RemoteIterator<PathBasedCacheDescriptor> dit
+        = dfs.listPathBasedCacheDescriptors(null, null);
+    for (int i=0; i<numEntries; i++) {
+      assertTrue("Unexpected # of cache entries: " + i, dit.hasNext());
+      PathBasedCacheDescriptor cd = dit.next();
+      assertEquals(i+1, cd.getEntryId());
+      assertEquals(entryPrefix + i, cd.getPath().toUri().getPath());
+      assertEquals(pool, cd.getPool());
+    }
+    assertFalse("Unexpected # of cache descriptors found", dit.hasNext());
+  
+    // Restart namenode
+    cluster.restartNameNode();
+  
+    // Check that state came back up
+    pit = dfs.listCachePools();
+    assertTrue("No cache pools found", pit.hasNext());
+    info = pit.next();
+    assertEquals(pool, info.getPoolName());
+    assertEquals(pool, info.getPoolName());
+    assertEquals(groupName, info.getGroupName());
+    assertEquals(mode, info.getMode());
+    assertEquals(weight, (int)info.getWeight());
+    assertFalse("Unexpected # of cache pools found", pit.hasNext());
+  
+    dit = dfs.listPathBasedCacheDescriptors(null, null);
+    for (int i=0; i<numEntries; i++) {
+      assertTrue("Unexpected # of cache entries: " + i, dit.hasNext());
+      PathBasedCacheDescriptor cd = dit.next();
+      assertEquals(i+1, cd.getEntryId());
+      assertEquals(entryPrefix + i, cd.getPath().toUri().getPath());
+      assertEquals(pool, cd.getPool());
+    }
+    assertFalse("Unexpected # of cache descriptors found", dit.hasNext());
+  }
+
+  private static void waitForCachedBlocks(NameNode nn,
+      final int expectedCachedBlocks, final int expectedCachedReplicas) 
+          throws Exception {
+    final FSNamesystem namesystem = nn.getNamesystem();
+    final CacheManager cacheManager = namesystem.getCacheManager();
+    LOG.info("Waiting for " + expectedCachedBlocks + " blocks with " +
+             expectedCachedReplicas + " replicas.");
+    GenericTestUtils.waitFor(new Supplier<Boolean>() {
+      @Override
+      public Boolean get() {
+        int numCachedBlocks = 0, numCachedReplicas = 0;
+        namesystem.readLock();
+        try {
+          GSet<CachedBlock, CachedBlock> cachedBlocks =
+              cacheManager.getCachedBlocks();
+          if (cachedBlocks != null) {
+            for (Iterator<CachedBlock> iter = cachedBlocks.iterator();
+                iter.hasNext(); ) {
+              CachedBlock cachedBlock = iter.next();
+              numCachedBlocks++;
+              numCachedReplicas += cachedBlock.getDatanodes(Type.CACHED).size();
+            }
+          }
+        } finally {
+          namesystem.readUnlock();
+        }
+        if ((numCachedBlocks == expectedCachedBlocks) && 
+            (numCachedReplicas == expectedCachedReplicas)) {
+          return true;
+        } else {
+          LOG.info("cached blocks: have " + numCachedBlocks +
+              " / " + expectedCachedBlocks);
+          LOG.info("cached replicas: have " + numCachedReplicas +
+              " / " + expectedCachedReplicas);
+          return false;
+        }
+      }
+    }, 500, 60000);
+  }
+
+  private static final long BLOCK_SIZE = 512;
+  private static final int NUM_DATANODES = 4;
+
+  // Most Linux installs will allow non-root users to lock 64KB.
+  private static final long CACHE_CAPACITY = 64 * 1024 / NUM_DATANODES;
+
+  /**
+   * Return true if we can test DN caching.
+   */
+  private static boolean canTestDatanodeCaching() {
+    if (!NativeIO.isAvailable()) {
+      // Need NativeIO in order to cache blocks on the DN.
+      return false;
+    }
+    if (NativeIO.getMemlockLimit() < CACHE_CAPACITY) {
+      return false;
+    }
+    return true;
+  }
+
+  private static HdfsConfiguration createCachingConf() {
+    HdfsConfiguration conf = new HdfsConfiguration();
+    conf.setLong(DFS_BLOCK_SIZE_KEY, BLOCK_SIZE);
+    conf.setLong(DFS_DATANODE_MAX_LOCKED_MEMORY_KEY, CACHE_CAPACITY);
+    conf.setLong(DFS_HEARTBEAT_INTERVAL_KEY, 1);
+    conf.setBoolean(DFS_NAMENODE_CACHING_ENABLED_KEY, true);
+    conf.setLong(DFS_CACHEREPORT_INTERVAL_MSEC_KEY, 1000);
+    conf.setLong(DFS_NAMENODE_PATH_BASED_CACHE_REFRESH_INTERVAL_MS, 1000);
+    return conf;
+  }
+
+  @Test(timeout=120000)
+  public void testWaitForCachedReplicas() throws Exception {
+    Assume.assumeTrue(canTestDatanodeCaching());
+    HdfsConfiguration conf = createCachingConf();
+    FileSystemTestHelper helper = new FileSystemTestHelper();
+    MiniDFSCluster cluster =
+      new MiniDFSCluster.Builder(conf).numDataNodes(NUM_DATANODES).build();
+
+    try {
+      cluster.waitActive();
+      DistributedFileSystem dfs = cluster.getFileSystem();
+      NameNode namenode = cluster.getNameNode();
+      NamenodeProtocols nnRpc = namenode.getRpcServer();
+      Path rootDir = helper.getDefaultWorkingDirectory(dfs);
+      // Create the pool
+      final String pool = "friendlyPool";
+      nnRpc.addCachePool(new CachePoolInfo("friendlyPool"));
+      // Create some test files
+      final int numFiles = 2;
+      final int numBlocksPerFile = 2;
+      final List<String> paths = new ArrayList<String>(numFiles);
+      for (int i=0; i<numFiles; i++) {
+        Path p = new Path(rootDir, "testCachePaths-" + i);
+        FileSystemTestHelper.createFile(dfs, p, numBlocksPerFile,
+            (int)BLOCK_SIZE);
+        paths.add(p.toUri().getPath());
+      }
+      // Check the initial statistics at the namenode
+      waitForCachedBlocks(namenode, 0, 0);
+      // Cache and check each path in sequence
+      int expected = 0;
+      for (int i=0; i<numFiles; i++) {
+        PathBasedCacheDirective directive =
+            new PathBasedCacheDirective.Builder().
+              setPath(new Path(paths.get(i))).
+              setPool(pool).
+              build();
+        PathBasedCacheDescriptor descriptor =
+            nnRpc.addPathBasedCacheDirective(directive);
+        assertEquals("Descriptor does not match requested path",
+            new Path(paths.get(i)), descriptor.getPath());
+        assertEquals("Descriptor does not match requested pool", pool,
+            descriptor.getPool());
+        expected += numBlocksPerFile;
+        waitForCachedBlocks(namenode, expected, expected);
+      }
+      // Uncache and check each path in sequence
+      RemoteIterator<PathBasedCacheDescriptor> entries =
+          nnRpc.listPathBasedCacheDescriptors(0, null, null);
+      for (int i=0; i<numFiles; i++) {
+        PathBasedCacheDescriptor descriptor = entries.next();
+        nnRpc.removePathBasedCacheDescriptor(descriptor.getEntryId());
+        expected -= numBlocksPerFile;
+        waitForCachedBlocks(namenode, expected, expected);
+      }
+    } finally {
+      cluster.shutdown();
+    }
+  }
+
+  @Test(timeout=120000)
+  public void testAddingPathBasedCacheDirectivesWhenCachingIsDisabled()
+      throws Exception {
+    Assume.assumeTrue(canTestDatanodeCaching());
+    HdfsConfiguration conf = createCachingConf();
+    conf.setBoolean(DFS_NAMENODE_CACHING_ENABLED_KEY, false);
+    MiniDFSCluster cluster =
+      new MiniDFSCluster.Builder(conf).numDataNodes(NUM_DATANODES).build();
+
+    try {
+      cluster.waitActive();
+      DistributedFileSystem dfs = cluster.getFileSystem();
+      NameNode namenode = cluster.getNameNode();
+      // Create the pool
+      String pool = "pool1";
+      namenode.getRpcServer().addCachePool(new CachePoolInfo(pool));
+      // Create some test files
+      final int numFiles = 2;
+      final int numBlocksPerFile = 2;
+      final List<String> paths = new ArrayList<String>(numFiles);
+      for (int i=0; i<numFiles; i++) {
+        Path p = new Path("/testCachePaths-" + i);
+        FileSystemTestHelper.createFile(dfs, p, numBlocksPerFile,
+            (int)BLOCK_SIZE);
+        paths.add(p.toUri().getPath());
+      }
+      // Check the initial statistics at the namenode
+      waitForCachedBlocks(namenode, 0, 0);
+      // Cache and check each path in sequence
+      int expected = 0;
+      for (int i=0; i<numFiles; i++) {
+        PathBasedCacheDirective directive =
+            new PathBasedCacheDirective.Builder().
+              setPath(new Path(paths.get(i))).
+              setPool(pool).
+              build();
+        dfs.addPathBasedCacheDirective(directive);
+        waitForCachedBlocks(namenode, expected, 0);
+      }
+      Thread.sleep(20000);
+      waitForCachedBlocks(namenode, expected, 0);
+    } finally {
+      cluster.shutdown();
+    }
+  }
+
+  @Test(timeout=120000)
+  public void testWaitForCachedReplicasInDirectory() throws Exception {
+    Assume.assumeTrue(canTestDatanodeCaching());
+    HdfsConfiguration conf = createCachingConf();
+    MiniDFSCluster cluster =
+      new MiniDFSCluster.Builder(conf).numDataNodes(NUM_DATANODES).build();
+
+    try {
+      cluster.waitActive();
+      DistributedFileSystem dfs = cluster.getFileSystem();
+      NameNode namenode = cluster.getNameNode();
+      // Create the pool
+      final String pool = "friendlyPool";
+      dfs.addCachePool(new CachePoolInfo(pool));
+      // Create some test files
+      final List<Path> paths = new LinkedList<Path>();
+      paths.add(new Path("/foo/bar"));
+      paths.add(new Path("/foo/baz"));
+      paths.add(new Path("/foo2/bar2"));
+      paths.add(new Path("/foo2/baz2"));
+      dfs.mkdir(new Path("/foo"), FsPermission.getDirDefault());
+      dfs.mkdir(new Path("/foo2"), FsPermission.getDirDefault());
+      final int numBlocksPerFile = 2;
+      for (Path path : paths) {
+        FileSystemTestHelper.createFile(dfs, path, numBlocksPerFile,
+            (int)BLOCK_SIZE, (short)3, false);
+      }
+      waitForCachedBlocks(namenode, 0, 0);
+      // cache entire directory
+      PathBasedCacheDescriptor descriptor = dfs.addPathBasedCacheDirective(
+            new PathBasedCacheDirective.Builder().
+              setPath(new Path("/foo")).
+              setReplication((short)2).
+              setPool(pool).
+              build());
+      assertEquals("Descriptor does not match requested pool", pool,
+          descriptor.getPool());
+      waitForCachedBlocks(namenode, 4, 8);
+      // remove and watch numCached go to 0
+      dfs.removePathBasedCacheDescriptor(descriptor);
+      waitForCachedBlocks(namenode, 0, 0);
+    } finally {
+      cluster.shutdown();
+    }
+  }
+
+}
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestRetryCacheWithHA.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestRetryCacheWithHA.java
index 82deab5..44f4e64 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestRetryCacheWithHA.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestRetryCacheWithHA.java
@@ -42,6 +42,7 @@
 import org.apache.hadoop.fs.FileStatus;
 import org.apache.hadoop.fs.Options.Rename;
 import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.fs.RemoteIterator;
 import org.apache.hadoop.fs.permission.FsPermission;
 import org.apache.hadoop.hdfs.DFSClient;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
@@ -53,12 +54,15 @@
 import org.apache.hadoop.hdfs.NameNodeProxies;
 import org.apache.hadoop.hdfs.client.HdfsDataOutputStream;
 import org.apache.hadoop.hdfs.client.HdfsDataOutputStream.SyncFlag;
+import org.apache.hadoop.hdfs.protocol.CachePoolInfo;
 import org.apache.hadoop.hdfs.protocol.ClientProtocol;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
 import org.apache.hadoop.hdfs.protocol.HdfsFileStatus;
 import org.apache.hadoop.hdfs.protocol.LocatedBlock;
 import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDescriptor;
+import org.apache.hadoop.hdfs.protocol.PathBasedCacheDirective;
 import org.apache.hadoop.hdfs.server.blockmanagement.BlockInfoUnderConstruction;
 import org.apache.hadoop.hdfs.server.namenode.FSNamesystem;
 import org.apache.hadoop.hdfs.server.namenode.INodeFile;
@@ -147,7 +151,7 @@
     FSNamesystem fsn0 = cluster.getNamesystem(0);
     LightWeightCache<CacheEntry, CacheEntry> cacheSet = 
         (LightWeightCache<CacheEntry, CacheEntry>) fsn0.getRetryCache().getCacheSet();
-    assertEquals(14, cacheSet.size());
+    assertEquals(19, cacheSet.size());
     
     Map<CacheEntry, CacheEntry> oldEntries = 
         new HashMap<CacheEntry, CacheEntry>();
@@ -168,7 +172,7 @@
     FSNamesystem fsn1 = cluster.getNamesystem(1);
     cacheSet = (LightWeightCache<CacheEntry, CacheEntry>) fsn1
         .getRetryCache().getCacheSet();
-    assertEquals(14, cacheSet.size());
+    assertEquals(19, cacheSet.size());
     iter = cacheSet.iterator();
     while (iter.hasNext()) {
       CacheEntry entry = iter.next();
@@ -733,6 +737,208 @@
     }
   }
   
+  /** addPathBasedCacheDirective */
+  class AddPathBasedCacheDirectiveOp extends AtMostOnceOp {
+    private String pool;
+    private String path;
+    private PathBasedCacheDescriptor descriptor;
+
+    AddPathBasedCacheDirectiveOp(DFSClient client, String pool, String path) {
+      super("addPathBasedCacheDirective", client);
+      this.pool = pool;
+      this.path = path;
+    }
+
+    @Override
+    void prepare() throws Exception {
+      dfs.addCachePool(new CachePoolInfo(pool));
+    }
+
+    @Override
+    void invoke() throws Exception {
+      descriptor = client.addPathBasedCacheDirective(
+          new PathBasedCacheDirective.Builder().
+              setPath(new Path(path)).
+              setPool(pool).
+              build());
+    }
+
+    @Override
+    boolean checkNamenodeBeforeReturn() throws Exception {
+      for (int i = 0; i < CHECKTIMES; i++) {
+        RemoteIterator<PathBasedCacheDescriptor> iter =
+            dfs.listPathBasedCacheDescriptors(pool, new Path(path));
+        if (iter.hasNext()) {
+          return true;
+        }
+        Thread.sleep(1000);
+      }
+      return false;
+    }
+
+    @Override
+    Object getResult() {
+      return descriptor;
+    }
+  }
+
+  /** removePathBasedCacheDescriptor */
+  class RemovePathBasedCacheDescriptorOp extends AtMostOnceOp {
+    private String pool;
+    private String path;
+    private PathBasedCacheDescriptor descriptor;
+
+    RemovePathBasedCacheDescriptorOp(DFSClient client, String pool,
+        String path) {
+      super("removePathBasedCacheDescriptor", client);
+      this.pool = pool;
+      this.path = path;
+    }
+
+    @Override
+    void prepare() throws Exception {
+      dfs.addCachePool(new CachePoolInfo(pool));
+      descriptor = dfs.addPathBasedCacheDirective(
+          new PathBasedCacheDirective.Builder().
+              setPath(new Path(path)).
+              setPool(pool).
+              build());
+    }
+
+    @Override
+    void invoke() throws Exception {
+      client.removePathBasedCacheDescriptor(descriptor.getEntryId());
+    }
+
+    @Override
+    boolean checkNamenodeBeforeReturn() throws Exception {
+      for (int i = 0; i < CHECKTIMES; i++) {
+        RemoteIterator<PathBasedCacheDescriptor> iter =
+            dfs.listPathBasedCacheDescriptors(pool, new Path(path));
+        if (!iter.hasNext()) {
+          return true;
+        }
+        Thread.sleep(1000);
+      }
+      return false;
+    }
+
+    @Override
+    Object getResult() {
+      return null;
+    }
+  }
+
+  /** addCachePool */
+  class AddCachePoolOp extends AtMostOnceOp {
+    private String pool;
+
+    AddCachePoolOp(DFSClient client, String pool) {
+      super("addCachePool", client);
+      this.pool = pool;
+    }
+
+    @Override
+    void prepare() throws Exception {
+    }
+
+    @Override
+    void invoke() throws Exception {
+      client.addCachePool(new CachePoolInfo(pool));
+    }
+
+    @Override
+    boolean checkNamenodeBeforeReturn() throws Exception {
+      for (int i = 0; i < CHECKTIMES; i++) {
+        RemoteIterator<CachePoolInfo> iter = dfs.listCachePools();
+        if (iter.hasNext()) {
+          return true;
+        }
+        Thread.sleep(1000);
+      }
+      return false;
+    }
+
+    @Override
+    Object getResult() {
+      return null;
+    }
+  }
+
+  /** modifyCachePool */
+  class ModifyCachePoolOp extends AtMostOnceOp {
+    String pool;
+
+    ModifyCachePoolOp(DFSClient client, String pool) {
+      super("modifyCachePool", client);
+      this.pool = pool;
+    }
+
+    @Override
+    void prepare() throws Exception {
+      client.addCachePool(new CachePoolInfo(pool).setWeight(10));
+    }
+
+    @Override
+    void invoke() throws Exception {
+      client.modifyCachePool(new CachePoolInfo(pool).setWeight(99));
+    }
+
+    @Override
+    boolean checkNamenodeBeforeReturn() throws Exception {
+      for (int i = 0; i < CHECKTIMES; i++) {
+        RemoteIterator<CachePoolInfo> iter = dfs.listCachePools();
+        if (iter.hasNext() && iter.next().getWeight() == 99) {
+          return true;
+        }
+        Thread.sleep(1000);
+      }
+      return false;
+    }
+
+    @Override
+    Object getResult() {
+      return null;
+    }
+  }
+
+  /** removeCachePool */
+  class RemoveCachePoolOp extends AtMostOnceOp {
+    private String pool;
+
+    RemoveCachePoolOp(DFSClient client, String pool) {
+      super("removeCachePool", client);
+      this.pool = pool;
+    }
+
+    @Override
+    void prepare() throws Exception {
+      client.addCachePool(new CachePoolInfo(pool));
+    }
+
+    @Override
+    void invoke() throws Exception {
+      client.removeCachePool(pool);
+    }
+
+    @Override
+    boolean checkNamenodeBeforeReturn() throws Exception {
+      for (int i = 0; i < CHECKTIMES; i++) {
+        RemoteIterator<CachePoolInfo> iter = dfs.listCachePools();
+        if (!iter.hasNext()) {
+          return true;
+        }
+        Thread.sleep(1000);
+      }
+      return false;
+    }
+
+    @Override
+    Object getResult() {
+      return null;
+    }
+  }
+
   @Test (timeout=60000)
   public void testCreateSnapshot() throws Exception {
     final DFSClient client = genClientWithDummyHandler();
@@ -810,6 +1016,42 @@
     testClientRetryWithFailover(op);
   }
   
+  @Test (timeout=60000)
+  public void testAddPathBasedCacheDirective() throws Exception {
+    DFSClient client = genClientWithDummyHandler();
+    AtMostOnceOp op = new AddPathBasedCacheDirectiveOp(client, "pool", "/path");
+    testClientRetryWithFailover(op);
+  }
+
+  @Test (timeout=60000)
+  public void testRemovePathBasedCacheDescriptor() throws Exception {
+    DFSClient client = genClientWithDummyHandler();
+    AtMostOnceOp op = new RemovePathBasedCacheDescriptorOp(client, "pool",
+        "/path");
+    testClientRetryWithFailover(op);
+  }
+
+  @Test (timeout=60000)
+  public void testAddCachePool() throws Exception {
+    DFSClient client = genClientWithDummyHandler();
+    AtMostOnceOp op = new AddCachePoolOp(client, "pool");
+    testClientRetryWithFailover(op);
+  }
+
+  @Test (timeout=60000)
+  public void testModifyCachePool() throws Exception {
+    DFSClient client = genClientWithDummyHandler();
+    AtMostOnceOp op = new ModifyCachePoolOp(client, "pool");
+    testClientRetryWithFailover(op);
+  }
+
+  @Test (timeout=60000)
+  public void testRemoveCachePool() throws Exception {
+    DFSClient client = genClientWithDummyHandler();
+    AtMostOnceOp op = new RemoveCachePoolOp(client, "pool");
+    testClientRetryWithFailover(op);
+  }
+
   /**
    * When NN failover happens, if the client did not receive the response and
    * send a retry request to the other NN, the same response should be recieved
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/web/TestJsonUtil.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/web/TestJsonUtil.java
index 0dc00a6..f4f7095 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/web/TestJsonUtil.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/web/TestJsonUtil.java
@@ -79,6 +79,8 @@
     response.put("xceiverCount", 4096l);
     response.put("networkLocation", "foo.bar.baz");
     response.put("adminState", "NORMAL");
+    response.put("cacheCapacity", 123l);
+    response.put("cacheUsed", 321l);
     
     JsonUtil.toDatanodeInfo(response);
   }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/resources/editsStored b/hadoop-hdfs-project/hadoop-hdfs/src/test/resources/editsStored
index 111cec0..17b95da 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/resources/editsStored
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/resources/editsStored
Binary files differ
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/resources/editsStored.xml b/hadoop-hdfs-project/hadoop-hdfs/src/test/resources/editsStored.xml
index dbb3498..f013c25 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/resources/editsStored.xml
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/resources/editsStored.xml
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <EDITS>
-  <EDITS_VERSION>-47</EDITS_VERSION>
+  <EDITS_VERSION>-48</EDITS_VERSION>
   <RECORD>
     <OPCODE>OP_START_LOG_SEGMENT</OPCODE>
     <DATA>
@@ -13,8 +13,8 @@
       <TXID>2</TXID>
       <DELEGATION_KEY>
         <KEY_ID>1</KEY_ID>
-        <EXPIRY_DATE>1375509063810</EXPIRY_DATE>
-        <KEY>4d47710649039b98</KEY>
+        <EXPIRY_DATE>1381946377599</EXPIRY_DATE>
+        <KEY>4f37c0db7342fb35</KEY>
       </DELEGATION_KEY>
     </DATA>
   </RECORD>
@@ -24,8 +24,8 @@
       <TXID>3</TXID>
       <DELEGATION_KEY>
         <KEY_ID>2</KEY_ID>
-        <EXPIRY_DATE>1375509063812</EXPIRY_DATE>
-        <KEY>38cbb1d8fd90fcb2</KEY>
+        <EXPIRY_DATE>1381946377609</EXPIRY_DATE>
+        <KEY>471d4ddd00402ba6</KEY>
       </DELEGATION_KEY>
     </DATA>
   </RECORD>
@@ -37,17 +37,17 @@
       <INODEID>16386</INODEID>
       <PATH>/file_create_u\0001;F431</PATH>
       <REPLICATION>1</REPLICATION>
-      <MTIME>1374817864805</MTIME>
-      <ATIME>1374817864805</ATIME>
+      <MTIME>1381255179312</MTIME>
+      <ATIME>1381255179312</ATIME>
       <BLOCKSIZE>512</BLOCKSIZE>
-      <CLIENT_NAME>DFSClient_NONMAPREDUCE_-1676409172_1</CLIENT_NAME>
+      <CLIENT_NAME>DFSClient_NONMAPREDUCE_-134124999_1</CLIENT_NAME>
       <CLIENT_MACHINE>127.0.0.1</CLIENT_MACHINE>
       <PERMISSION_STATUS>
-        <USERNAME>jing</USERNAME>
+        <USERNAME>andrew</USERNAME>
         <GROUPNAME>supergroup</GROUPNAME>
         <MODE>420</MODE>
       </PERMISSION_STATUS>
-      <RPC_CLIENTID>5245793a-984b-4264-8d7c-7890775547a0</RPC_CLIENTID>
+      <RPC_CLIENTID>27ac79f0-d378-4933-824b-c2a188968d97</RPC_CLIENTID>
       <RPC_CALLID>8</RPC_CALLID>
     </DATA>
   </RECORD>
@@ -59,13 +59,13 @@
       <INODEID>0</INODEID>
       <PATH>/file_create_u\0001;F431</PATH>
       <REPLICATION>1</REPLICATION>
-      <MTIME>1374817864816</MTIME>
-      <ATIME>1374817864805</ATIME>
+      <MTIME>1381255179355</MTIME>
+      <ATIME>1381255179312</ATIME>
       <BLOCKSIZE>512</BLOCKSIZE>
       <CLIENT_NAME></CLIENT_NAME>
       <CLIENT_MACHINE></CLIENT_MACHINE>
       <PERMISSION_STATUS>
-        <USERNAME>jing</USERNAME>
+        <USERNAME>andrew</USERNAME>
         <GROUPNAME>supergroup</GROUPNAME>
         <MODE>420</MODE>
       </PERMISSION_STATUS>
@@ -78,8 +78,8 @@
       <LENGTH>0</LENGTH>
       <SRC>/file_create_u\0001;F431</SRC>
       <DST>/file_moved</DST>
-      <TIMESTAMP>1374817864818</TIMESTAMP>
-      <RPC_CLIENTID>5245793a-984b-4264-8d7c-7890775547a0</RPC_CLIENTID>
+      <TIMESTAMP>1381255179373</TIMESTAMP>
+      <RPC_CLIENTID>27ac79f0-d378-4933-824b-c2a188968d97</RPC_CLIENTID>
       <RPC_CALLID>10</RPC_CALLID>
     </DATA>
   </RECORD>
@@ -89,8 +89,8 @@
       <TXID>7</TXID>
       <LENGTH>0</LENGTH>
       <PATH>/file_moved</PATH>
-      <TIMESTAMP>1374817864822</TIMESTAMP>
-      <RPC_CLIENTID>5245793a-984b-4264-8d7c-7890775547a0</RPC_CLIENTID>
+      <TIMESTAMP>1381255179397</TIMESTAMP>
+      <RPC_CLIENTID>27ac79f0-d378-4933-824b-c2a188968d97</RPC_CLIENTID>
       <RPC_CALLID>11</RPC_CALLID>
     </DATA>
   </RECORD>
@@ -101,9 +101,9 @@
       <LENGTH>0</LENGTH>
       <INODEID>16387</INODEID>
       <PATH>/directory_mkdir</PATH>
-      <TIMESTAMP>1374817864825</TIMESTAMP>
+      <TIMESTAMP>1381255179424</TIMESTAMP>
       <PERMISSION_STATUS>
-        <USERNAME>jing</USERNAME>
+        <USERNAME>andrew</USERNAME>
         <GROUPNAME>supergroup</GROUPNAME>
         <MODE>493</MODE>
       </PERMISSION_STATUS>
@@ -136,7 +136,7 @@
       <TXID>12</TXID>
       <SNAPSHOTROOT>/directory_mkdir</SNAPSHOTROOT>
       <SNAPSHOTNAME>snapshot1</SNAPSHOTNAME>
-      <RPC_CLIENTID>5245793a-984b-4264-8d7c-7890775547a0</RPC_CLIENTID>
+      <RPC_CLIENTID>27ac79f0-d378-4933-824b-c2a188968d97</RPC_CLIENTID>
       <RPC_CALLID>16</RPC_CALLID>
     </DATA>
   </RECORD>
@@ -147,7 +147,7 @@
       <SNAPSHOTROOT>/directory_mkdir</SNAPSHOTROOT>
       <SNAPSHOTOLDNAME>snapshot1</SNAPSHOTOLDNAME>
       <SNAPSHOTNEWNAME>snapshot2</SNAPSHOTNEWNAME>
-      <RPC_CLIENTID>5245793a-984b-4264-8d7c-7890775547a0</RPC_CLIENTID>
+      <RPC_CLIENTID>27ac79f0-d378-4933-824b-c2a188968d97</RPC_CLIENTID>
       <RPC_CALLID>17</RPC_CALLID>
     </DATA>
   </RECORD>
@@ -157,7 +157,7 @@
       <TXID>14</TXID>
       <SNAPSHOTROOT>/directory_mkdir</SNAPSHOTROOT>
       <SNAPSHOTNAME>snapshot2</SNAPSHOTNAME>
-      <RPC_CLIENTID>5245793a-984b-4264-8d7c-7890775547a0</RPC_CLIENTID>
+      <RPC_CLIENTID>27ac79f0-d378-4933-824b-c2a188968d97</RPC_CLIENTID>
       <RPC_CALLID>18</RPC_CALLID>
     </DATA>
   </RECORD>
@@ -169,17 +169,17 @@
       <INODEID>16388</INODEID>
       <PATH>/file_create_u\0001;F431</PATH>
       <REPLICATION>1</REPLICATION>
-      <MTIME>1374817864846</MTIME>
-      <ATIME>1374817864846</ATIME>
+      <MTIME>1381255179522</MTIME>
+      <ATIME>1381255179522</ATIME>
       <BLOCKSIZE>512</BLOCKSIZE>
-      <CLIENT_NAME>DFSClient_NONMAPREDUCE_-1676409172_1</CLIENT_NAME>
+      <CLIENT_NAME>DFSClient_NONMAPREDUCE_-134124999_1</CLIENT_NAME>
       <CLIENT_MACHINE>127.0.0.1</CLIENT_MACHINE>
       <PERMISSION_STATUS>
-        <USERNAME>jing</USERNAME>
+        <USERNAME>andrew</USERNAME>
         <GROUPNAME>supergroup</GROUPNAME>
         <MODE>420</MODE>
       </PERMISSION_STATUS>
-      <RPC_CLIENTID>5245793a-984b-4264-8d7c-7890775547a0</RPC_CLIENTID>
+      <RPC_CLIENTID>27ac79f0-d378-4933-824b-c2a188968d97</RPC_CLIENTID>
       <RPC_CALLID>19</RPC_CALLID>
     </DATA>
   </RECORD>
@@ -191,13 +191,13 @@
       <INODEID>0</INODEID>
       <PATH>/file_create_u\0001;F431</PATH>
       <REPLICATION>1</REPLICATION>
-      <MTIME>1374817864848</MTIME>
-      <ATIME>1374817864846</ATIME>
+      <MTIME>1381255179531</MTIME>
+      <ATIME>1381255179522</ATIME>
       <BLOCKSIZE>512</BLOCKSIZE>
       <CLIENT_NAME></CLIENT_NAME>
       <CLIENT_MACHINE></CLIENT_MACHINE>
       <PERMISSION_STATUS>
-        <USERNAME>jing</USERNAME>
+        <USERNAME>andrew</USERNAME>
         <GROUPNAME>supergroup</GROUPNAME>
         <MODE>420</MODE>
       </PERMISSION_STATUS>
@@ -253,9 +253,9 @@
       <LENGTH>0</LENGTH>
       <SRC>/file_create_u\0001;F431</SRC>
       <DST>/file_moved</DST>
-      <TIMESTAMP>1374817864860</TIMESTAMP>
+      <TIMESTAMP>1381255179602</TIMESTAMP>
       <OPTIONS>NONE</OPTIONS>
-      <RPC_CLIENTID>5245793a-984b-4264-8d7c-7890775547a0</RPC_CLIENTID>
+      <RPC_CLIENTID>27ac79f0-d378-4933-824b-c2a188968d97</RPC_CLIENTID>
       <RPC_CALLID>26</RPC_CALLID>
     </DATA>
   </RECORD>
@@ -267,17 +267,17 @@
       <INODEID>16389</INODEID>
       <PATH>/file_concat_target</PATH>
       <REPLICATION>1</REPLICATION>
-      <MTIME>1374817864864</MTIME>
-      <ATIME>1374817864864</ATIME>
+      <MTIME>1381255179619</MTIME>
+      <ATIME>1381255179619</ATIME>
       <BLOCKSIZE>512</BLOCKSIZE>
-      <CLIENT_NAME>DFSClient_NONMAPREDUCE_-1676409172_1</CLIENT_NAME>
+      <CLIENT_NAME>DFSClient_NONMAPREDUCE_-134124999_1</CLIENT_NAME>
       <CLIENT_MACHINE>127.0.0.1</CLIENT_MACHINE>
       <PERMISSION_STATUS>
-        <USERNAME>jing</USERNAME>
+        <USERNAME>andrew</USERNAME>
         <GROUPNAME>supergroup</GROUPNAME>
         <MODE>420</MODE>
       </PERMISSION_STATUS>
-      <RPC_CLIENTID>5245793a-984b-4264-8d7c-7890775547a0</RPC_CLIENTID>
+      <RPC_CLIENTID>27ac79f0-d378-4933-824b-c2a188968d97</RPC_CLIENTID>
       <RPC_CALLID>28</RPC_CALLID>
     </DATA>
   </RECORD>
@@ -388,8 +388,8 @@
       <INODEID>0</INODEID>
       <PATH>/file_concat_target</PATH>
       <REPLICATION>1</REPLICATION>
-      <MTIME>1374817864927</MTIME>
-      <ATIME>1374817864864</ATIME>
+      <MTIME>1381255179862</MTIME>
+      <ATIME>1381255179619</ATIME>
       <BLOCKSIZE>512</BLOCKSIZE>
       <CLIENT_NAME></CLIENT_NAME>
       <CLIENT_MACHINE></CLIENT_MACHINE>
@@ -409,7 +409,7 @@
         <GENSTAMP>1003</GENSTAMP>
       </BLOCK>
       <PERMISSION_STATUS>
-        <USERNAME>jing</USERNAME>
+        <USERNAME>andrew</USERNAME>
         <GROUPNAME>supergroup</GROUPNAME>
         <MODE>420</MODE>
       </PERMISSION_STATUS>
@@ -423,17 +423,17 @@
       <INODEID>16390</INODEID>
       <PATH>/file_concat_0</PATH>
       <REPLICATION>1</REPLICATION>
-      <MTIME>1374817864929</MTIME>
-      <ATIME>1374817864929</ATIME>
+      <MTIME>1381255179876</MTIME>
+      <ATIME>1381255179876</ATIME>
       <BLOCKSIZE>512</BLOCKSIZE>
-      <CLIENT_NAME>DFSClient_NONMAPREDUCE_-1676409172_1</CLIENT_NAME>
+      <CLIENT_NAME>DFSClient_NONMAPREDUCE_-134124999_1</CLIENT_NAME>
       <CLIENT_MACHINE>127.0.0.1</CLIENT_MACHINE>
       <PERMISSION_STATUS>
-        <USERNAME>jing</USERNAME>
+        <USERNAME>andrew</USERNAME>
         <GROUPNAME>supergroup</GROUPNAME>
         <MODE>420</MODE>
       </PERMISSION_STATUS>
-      <RPC_CLIENTID>5245793a-984b-4264-8d7c-7890775547a0</RPC_CLIENTID>
+      <RPC_CLIENTID>27ac79f0-d378-4933-824b-c2a188968d97</RPC_CLIENTID>
       <RPC_CALLID>41</RPC_CALLID>
     </DATA>
   </RECORD>
@@ -544,8 +544,8 @@
       <INODEID>0</INODEID>
       <PATH>/file_concat_0</PATH>
       <REPLICATION>1</REPLICATION>
-      <MTIME>1374817864947</MTIME>
-      <ATIME>1374817864929</ATIME>
+      <MTIME>1381255179957</MTIME>
+      <ATIME>1381255179876</ATIME>
       <BLOCKSIZE>512</BLOCKSIZE>
       <CLIENT_NAME></CLIENT_NAME>
       <CLIENT_MACHINE></CLIENT_MACHINE>
@@ -565,7 +565,7 @@
         <GENSTAMP>1006</GENSTAMP>
       </BLOCK>
       <PERMISSION_STATUS>
-        <USERNAME>jing</USERNAME>
+        <USERNAME>andrew</USERNAME>
         <GROUPNAME>supergroup</GROUPNAME>
         <MODE>420</MODE>
       </PERMISSION_STATUS>
@@ -579,17 +579,17 @@
       <INODEID>16391</INODEID>
       <PATH>/file_concat_1</PATH>
       <REPLICATION>1</REPLICATION>
-      <MTIME>1374817864950</MTIME>
-      <ATIME>1374817864950</ATIME>
+      <MTIME>1381255179967</MTIME>
+      <ATIME>1381255179967</ATIME>
       <BLOCKSIZE>512</BLOCKSIZE>
-      <CLIENT_NAME>DFSClient_NONMAPREDUCE_-1676409172_1</CLIENT_NAME>
+      <CLIENT_NAME>DFSClient_NONMAPREDUCE_-134124999_1</CLIENT_NAME>
       <CLIENT_MACHINE>127.0.0.1</CLIENT_MACHINE>
       <PERMISSION_STATUS>
-        <USERNAME>jing</USERNAME>
+        <USERNAME>andrew</USERNAME>
         <GROUPNAME>supergroup</GROUPNAME>
         <MODE>420</MODE>
       </PERMISSION_STATUS>
-      <RPC_CLIENTID>5245793a-984b-4264-8d7c-7890775547a0</RPC_CLIENTID>
+      <RPC_CLIENTID>27ac79f0-d378-4933-824b-c2a188968d97</RPC_CLIENTID>
       <RPC_CALLID>53</RPC_CALLID>
     </DATA>
   </RECORD>
@@ -700,8 +700,8 @@
       <INODEID>0</INODEID>
       <PATH>/file_concat_1</PATH>
       <REPLICATION>1</REPLICATION>
-      <MTIME>1374817864966</MTIME>
-      <ATIME>1374817864950</ATIME>
+      <MTIME>1381255180085</MTIME>
+      <ATIME>1381255179967</ATIME>
       <BLOCKSIZE>512</BLOCKSIZE>
       <CLIENT_NAME></CLIENT_NAME>
       <CLIENT_MACHINE></CLIENT_MACHINE>
@@ -721,7 +721,7 @@
         <GENSTAMP>1009</GENSTAMP>
       </BLOCK>
       <PERMISSION_STATUS>
-        <USERNAME>jing</USERNAME>
+        <USERNAME>andrew</USERNAME>
         <GROUPNAME>supergroup</GROUPNAME>
         <MODE>420</MODE>
       </PERMISSION_STATUS>
@@ -733,12 +733,12 @@
       <TXID>56</TXID>
       <LENGTH>0</LENGTH>
       <TRG>/file_concat_target</TRG>
-      <TIMESTAMP>1374817864967</TIMESTAMP>
+      <TIMESTAMP>1381255180099</TIMESTAMP>
       <SOURCES>
         <SOURCE1>/file_concat_0</SOURCE1>
         <SOURCE2>/file_concat_1</SOURCE2>
       </SOURCES>
-      <RPC_CLIENTID>5245793a-984b-4264-8d7c-7890775547a0</RPC_CLIENTID>
+      <RPC_CLIENTID>27ac79f0-d378-4933-824b-c2a188968d97</RPC_CLIENTID>
       <RPC_CALLID>64</RPC_CALLID>
     </DATA>
   </RECORD>
@@ -750,14 +750,14 @@
       <INODEID>16392</INODEID>
       <PATH>/file_symlink</PATH>
       <VALUE>/file_concat_target</VALUE>
-      <MTIME>1374817864971</MTIME>
-      <ATIME>1374817864971</ATIME>
+      <MTIME>1381255180116</MTIME>
+      <ATIME>1381255180116</ATIME>
       <PERMISSION_STATUS>
-        <USERNAME>jing</USERNAME>
+        <USERNAME>andrew</USERNAME>
         <GROUPNAME>supergroup</GROUPNAME>
         <MODE>511</MODE>
       </PERMISSION_STATUS>
-      <RPC_CLIENTID>5245793a-984b-4264-8d7c-7890775547a0</RPC_CLIENTID>
+      <RPC_CLIENTID>27ac79f0-d378-4933-824b-c2a188968d97</RPC_CLIENTID>
       <RPC_CALLID>65</RPC_CALLID>
     </DATA>
   </RECORD>
@@ -768,14 +768,14 @@
       <DELEGATION_TOKEN_IDENTIFIER>
         <KIND>HDFS_DELEGATION_TOKEN</KIND>
         <SEQUENCE_NUMBER>1</SEQUENCE_NUMBER>
-        <OWNER>jing</OWNER>
+        <OWNER>andrew</OWNER>
         <RENEWER>JobTracker</RENEWER>
         <REALUSER></REALUSER>
-        <ISSUE_DATE>1374817864974</ISSUE_DATE>
-        <MAX_DATE>1375422664974</MAX_DATE>
+        <ISSUE_DATE>1381255180128</ISSUE_DATE>
+        <MAX_DATE>1381859980128</MAX_DATE>
         <MASTER_KEY_ID>2</MASTER_KEY_ID>
       </DELEGATION_TOKEN_IDENTIFIER>
-      <EXPIRY_TIME>1374904264974</EXPIRY_TIME>
+      <EXPIRY_TIME>1381341580128</EXPIRY_TIME>
     </DATA>
   </RECORD>
   <RECORD>
@@ -785,14 +785,14 @@
       <DELEGATION_TOKEN_IDENTIFIER>
         <KIND>HDFS_DELEGATION_TOKEN</KIND>
         <SEQUENCE_NUMBER>1</SEQUENCE_NUMBER>
-        <OWNER>jing</OWNER>
+        <OWNER>andrew</OWNER>
         <RENEWER>JobTracker</RENEWER>
         <REALUSER></REALUSER>
-        <ISSUE_DATE>1374817864974</ISSUE_DATE>
-        <MAX_DATE>1375422664974</MAX_DATE>
+        <ISSUE_DATE>1381255180128</ISSUE_DATE>
+        <MAX_DATE>1381859980128</MAX_DATE>
         <MASTER_KEY_ID>2</MASTER_KEY_ID>
       </DELEGATION_TOKEN_IDENTIFIER>
-      <EXPIRY_TIME>1374904265012</EXPIRY_TIME>
+      <EXPIRY_TIME>1381341580177</EXPIRY_TIME>
     </DATA>
   </RECORD>
   <RECORD>
@@ -802,55 +802,112 @@
       <DELEGATION_TOKEN_IDENTIFIER>
         <KIND>HDFS_DELEGATION_TOKEN</KIND>
         <SEQUENCE_NUMBER>1</SEQUENCE_NUMBER>
-        <OWNER>jing</OWNER>
+        <OWNER>andrew</OWNER>
         <RENEWER>JobTracker</RENEWER>
         <REALUSER></REALUSER>
-        <ISSUE_DATE>1374817864974</ISSUE_DATE>
-        <MAX_DATE>1375422664974</MAX_DATE>
+        <ISSUE_DATE>1381255180128</ISSUE_DATE>
+        <MAX_DATE>1381859980128</MAX_DATE>
         <MASTER_KEY_ID>2</MASTER_KEY_ID>
       </DELEGATION_TOKEN_IDENTIFIER>
     </DATA>
   </RECORD>
   <RECORD>
-    <OPCODE>OP_ADD</OPCODE>
+    <OPCODE>OP_ADD_CACHE_POOL</OPCODE>
     <DATA>
       <TXID>61</TXID>
+      <POOLNAME>poolparty</POOLNAME>
+      <PERMISSION_STATUS>
+        <USERNAME>andrew</USERNAME>
+        <GROUPNAME>andrew</GROUPNAME>
+        <MODE>493</MODE>
+      </PERMISSION_STATUS>
+      <WEIGHT>100</WEIGHT>
+      <RPC_CLIENTID>27ac79f0-d378-4933-824b-c2a188968d97</RPC_CLIENTID>
+      <RPC_CALLID>75</RPC_CALLID>
+    </DATA>
+  </RECORD>
+  <RECORD>
+    <OPCODE>OP_MODIFY_CACHE_POOL</OPCODE>
+    <DATA>
+      <TXID>62</TXID>
+      <POOLNAME>poolparty</POOLNAME>
+      <OWNERNAME>carlton</OWNERNAME>
+      <GROUPNAME>party</GROUPNAME>
+      <MODE>448</MODE>
+      <WEIGHT>1989</WEIGHT>
+      <RPC_CLIENTID>27ac79f0-d378-4933-824b-c2a188968d97</RPC_CLIENTID>
+      <RPC_CALLID>76</RPC_CALLID>
+    </DATA>
+  </RECORD>
+  <RECORD>
+    <OPCODE>OP_ADD_PATH_BASED_CACHE_DIRECTIVE</OPCODE>
+    <DATA>
+      <TXID>63</TXID>
+      <PATH>/bar</PATH>
+      <REPLICATION>1</REPLICATION>
+      <POOL>poolparty</POOL>
+      <RPC_CLIENTID>27ac79f0-d378-4933-824b-c2a188968d97</RPC_CLIENTID>
+      <RPC_CALLID>77</RPC_CALLID>
+    </DATA>
+  </RECORD>
+  <RECORD>
+    <OPCODE>OP_REMOVE_PATH_BASED_CACHE_DESCRIPTOR</OPCODE>
+    <DATA>
+      <TXID>64</TXID>
+      <ID>1</ID>
+      <RPC_CLIENTID>27ac79f0-d378-4933-824b-c2a188968d97</RPC_CLIENTID>
+      <RPC_CALLID>78</RPC_CALLID>
+    </DATA>
+  </RECORD>
+  <RECORD>
+    <OPCODE>OP_REMOVE_CACHE_POOL</OPCODE>
+    <DATA>
+      <TXID>65</TXID>
+      <POOLNAME>poolparty</POOLNAME>
+      <RPC_CLIENTID>27ac79f0-d378-4933-824b-c2a188968d97</RPC_CLIENTID>
+      <RPC_CALLID>79</RPC_CALLID>
+    </DATA>
+  </RECORD>
+  <RECORD>
+    <OPCODE>OP_ADD</OPCODE>
+    <DATA>
+      <TXID>66</TXID>
       <LENGTH>0</LENGTH>
       <INODEID>16393</INODEID>
       <PATH>/hard-lease-recovery-test</PATH>
       <REPLICATION>1</REPLICATION>
-      <MTIME>1374817865017</MTIME>
-      <ATIME>1374817865017</ATIME>
+      <MTIME>1381255180288</MTIME>
+      <ATIME>1381255180288</ATIME>
       <BLOCKSIZE>512</BLOCKSIZE>
-      <CLIENT_NAME>DFSClient_NONMAPREDUCE_-1676409172_1</CLIENT_NAME>
+      <CLIENT_NAME>DFSClient_NONMAPREDUCE_-134124999_1</CLIENT_NAME>
       <CLIENT_MACHINE>127.0.0.1</CLIENT_MACHINE>
       <PERMISSION_STATUS>
-        <USERNAME>jing</USERNAME>
+        <USERNAME>andrew</USERNAME>
         <GROUPNAME>supergroup</GROUPNAME>
         <MODE>420</MODE>
       </PERMISSION_STATUS>
-      <RPC_CLIENTID>5245793a-984b-4264-8d7c-7890775547a0</RPC_CLIENTID>
-      <RPC_CALLID>69</RPC_CALLID>
+      <RPC_CLIENTID>27ac79f0-d378-4933-824b-c2a188968d97</RPC_CLIENTID>
+      <RPC_CALLID>74</RPC_CALLID>
     </DATA>
   </RECORD>
   <RECORD>
     <OPCODE>OP_ALLOCATE_BLOCK_ID</OPCODE>
     <DATA>
-      <TXID>62</TXID>
+      <TXID>67</TXID>
       <BLOCK_ID>1073741834</BLOCK_ID>
     </DATA>
   </RECORD>
   <RECORD>
     <OPCODE>OP_SET_GENSTAMP_V2</OPCODE>
     <DATA>
-      <TXID>63</TXID>
+      <TXID>68</TXID>
       <GENSTAMPV2>1010</GENSTAMPV2>
     </DATA>
   </RECORD>
   <RECORD>
     <OPCODE>OP_UPDATE_BLOCKS</OPCODE>
     <DATA>
-      <TXID>64</TXID>
+      <TXID>69</TXID>
       <PATH>/hard-lease-recovery-test</PATH>
       <BLOCK>
         <BLOCK_ID>1073741834</BLOCK_ID>
@@ -864,7 +921,7 @@
   <RECORD>
     <OPCODE>OP_UPDATE_BLOCKS</OPCODE>
     <DATA>
-      <TXID>65</TXID>
+      <TXID>70</TXID>
       <PATH>/hard-lease-recovery-test</PATH>
       <BLOCK>
         <BLOCK_ID>1073741834</BLOCK_ID>
@@ -878,15 +935,31 @@
   <RECORD>
     <OPCODE>OP_SET_GENSTAMP_V2</OPCODE>
     <DATA>
-      <TXID>66</TXID>
+      <TXID>71</TXID>
       <GENSTAMPV2>1011</GENSTAMPV2>
     </DATA>
   </RECORD>
   <RECORD>
     <OPCODE>OP_REASSIGN_LEASE</OPCODE>
     <DATA>
-      <TXID>67</TXID>
-      <LEASEHOLDER>DFSClient_NONMAPREDUCE_-1676409172_1</LEASEHOLDER>
+      <TXID>72</TXID>
+      <LEASEHOLDER>DFSClient_NONMAPREDUCE_-134124999_1</LEASEHOLDER>
+      <PATH>/hard-lease-recovery-test</PATH>
+      <NEWHOLDER>HDFS_NameNode</NEWHOLDER>
+    </DATA>
+  </RECORD>
+  <RECORD>
+    <OPCODE>OP_SET_GENSTAMP_V2</OPCODE>
+    <DATA>
+      <TXID>73</TXID>
+      <GENSTAMPV2>1012</GENSTAMPV2>
+    </DATA>
+  </RECORD>
+  <RECORD>
+    <OPCODE>OP_REASSIGN_LEASE</OPCODE>
+    <DATA>
+      <TXID>74</TXID>
+      <LEASEHOLDER>HDFS_NameNode</LEASEHOLDER>
       <PATH>/hard-lease-recovery-test</PATH>
       <NEWHOLDER>HDFS_NameNode</NEWHOLDER>
     </DATA>
@@ -894,23 +967,23 @@
   <RECORD>
     <OPCODE>OP_CLOSE</OPCODE>
     <DATA>
-      <TXID>68</TXID>
+      <TXID>75</TXID>
       <LENGTH>0</LENGTH>
       <INODEID>0</INODEID>
       <PATH>/hard-lease-recovery-test</PATH>
       <REPLICATION>1</REPLICATION>
-      <MTIME>1374817867688</MTIME>
-      <ATIME>1374817865017</ATIME>
+      <MTIME>1381255185142</MTIME>
+      <ATIME>1381255180288</ATIME>
       <BLOCKSIZE>512</BLOCKSIZE>
       <CLIENT_NAME></CLIENT_NAME>
       <CLIENT_MACHINE></CLIENT_MACHINE>
       <BLOCK>
         <BLOCK_ID>1073741834</BLOCK_ID>
         <NUM_BYTES>11</NUM_BYTES>
-        <GENSTAMP>1011</GENSTAMP>
+        <GENSTAMP>1012</GENSTAMP>
       </BLOCK>
       <PERMISSION_STATUS>
-        <USERNAME>jing</USERNAME>
+        <USERNAME>andrew</USERNAME>
         <GROUPNAME>supergroup</GROUPNAME>
         <MODE>420</MODE>
       </PERMISSION_STATUS>
@@ -919,7 +992,7 @@
   <RECORD>
     <OPCODE>OP_END_LOG_SEGMENT</OPCODE>
     <DATA>
-      <TXID>69</TXID>
+      <TXID>76</TXID>
     </DATA>
   </RECORD>
 </EDITS>
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/resources/testCacheAdminConf.xml b/hadoop-hdfs-project/hadoop-hdfs/src/test/resources/testCacheAdminConf.xml
new file mode 100644
index 0000000..b3edc17
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/resources/testCacheAdminConf.xml
@@ -0,0 +1,362 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<?xml-stylesheet type="text/xsl" href="testConf.xsl"?>
+
+<!--
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You under the Apache License, Version 2.0
+   (the "License"); you may not use this file except in compliance with
+   the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+-->
+
+<configuration>
+  <!-- Normal mode is test. To run just the commands and dump the output
+       to the log, set it to nocompare -->
+  <mode>test</mode>
+  
+  <!--  Comparator types:
+           ExactComparator
+           SubstringComparator
+           RegexpComparator
+           TokenComparator
+           -->
+  <tests>
+
+    <test> <!--Tested -->
+      <description>Testing basic usage</description>
+      <test-commands>
+        <cache-admin-command></cache-admin-command>
+      </test-commands>
+      <cleanup-commands>
+      </cleanup-commands>
+      <comparators>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>Usage: bin/hdfs cacheadmin [COMMAND]</expected-output>
+        </comparator>
+      </comparators>
+    </test>
+
+    <test> <!--Tested -->
+      <description>Testing listing no cache pools</description>
+      <test-commands>
+        <cache-admin-command>-listPools</cache-admin-command>
+      </test-commands>
+      <cleanup-commands>
+      </cleanup-commands>
+      <comparators>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>Found 0 results.</expected-output>
+        </comparator>
+      </comparators>
+    </test>
+
+    <test> <!--Tested -->
+      <description>Testing adding a cache pool</description>
+      <test-commands>
+        <cache-admin-command>-addPool foo</cache-admin-command>
+      </test-commands>
+      <cleanup-commands>
+        <cache-admin-command>-removePool foo</cache-admin-command>
+      </cleanup-commands>
+      <comparators>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>Successfully added cache pool foo.</expected-output>
+        </comparator>
+      </comparators>
+    </test>
+
+    <test> <!--Tested -->
+      <description>Testing modifying a cache pool</description>
+      <test-commands>
+        <cache-admin-command>-addPool poolparty -owner alice -group alicegroup -mode 0000 -weight 50</cache-admin-command>
+        <cache-admin-command>-modifyPool poolparty -owner bob -group bobgroup -mode 0777 -weight 51</cache-admin-command>
+        <cache-admin-command>-listPools</cache-admin-command>
+      </test-commands>
+      <cleanup-commands>
+        <cache-admin-command>-removePool poolparty</cache-admin-command>
+      </cleanup-commands>
+      <comparators>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>poolparty  bob    bobgroup  rwxrwxrwx  51</expected-output>
+        </comparator>
+      </comparators>
+    </test>
+
+    <test> <!--Tested -->
+      <description>Testing deleting a cache pool</description>
+      <test-commands>
+        <cache-admin-command>-addPool foo</cache-admin-command>
+        <cache-admin-command>-removePool foo</cache-admin-command>
+      </test-commands>
+      <cleanup-commands>
+      </cleanup-commands>
+      <comparators>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>Successfully removed cache pool foo.</expected-output>
+        </comparator>
+      </comparators>
+    </test>
+
+    <test> <!--Tested -->
+      <description>Testing listing all cache pools</description>
+      <test-commands>
+        <cache-admin-command>-addPool foo -owner bob -group bob -mode 0664</cache-admin-command>
+        <cache-admin-command>-addPool bar -owner alice -group alicegroup -mode 0755</cache-admin-command>
+        <cache-admin-command>-listPools</cache-admin-command>
+      </test-commands>
+      <cleanup-commands>
+        <cache-admin-command>-removePool foo</cache-admin-command>
+        <cache-admin-command>-removePool bar</cache-admin-command>
+      </cleanup-commands>
+      <comparators>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>Found 2 results.</expected-output>
+        </comparator>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>bar   alice  alicegroup  rwxr-xr-x  100    </expected-output>
+        </comparator>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>foo   bob    bob         rw-rw-r--  100    </expected-output>
+        </comparator>
+      </comparators>
+    </test>
+
+    <test> <!--Tested -->
+      <description>Testing listing a single cache pool</description>
+      <test-commands>
+        <cache-admin-command>-addPool foo -owner bob -group bob -mode 0664</cache-admin-command>
+        <cache-admin-command>-addPool bar -owner alice -group alicegroup -mode 0755</cache-admin-command>
+        <cache-admin-command>-listPools foo</cache-admin-command>
+      </test-commands>
+      <cleanup-commands>
+        <cache-admin-command>-removePool foo</cache-admin-command>
+        <cache-admin-command>-removePool bar</cache-admin-command>
+      </cleanup-commands>
+      <comparators>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>Found 1 result.</expected-output>
+        </comparator>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>foo   bob    bob    rw-rw-r--  100    </expected-output>
+        </comparator>
+      </comparators>
+    </test>
+
+    <test> <!--Tested -->
+      <description>Testing creating cache paths</description>
+      <test-commands>
+        <cache-admin-command>-addPool pool1</cache-admin-command>
+        <cache-admin-command>-addDirective -path /foo -pool pool1</cache-admin-command>
+        <cache-admin-command>-addDirective -path /bar -pool pool1</cache-admin-command>
+        <cache-admin-command>-addDirective -path /baz -replication 2 -pool pool1</cache-admin-command>
+        <cache-admin-command>-listDirectives -pool pool1</cache-admin-command>
+      </test-commands>
+      <cleanup-commands>
+        <cache-admin-command>-removePool pool1</cache-admin-command>
+      </cleanup-commands>
+      <comparators>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>Found 3 entries</expected-output>
+        </comparator>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>1   pool1  /foo</expected-output>
+        </comparator>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>2   pool1  /bar</expected-output>
+        </comparator>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>3   pool1  /baz</expected-output>
+        </comparator>
+      </comparators>
+    </test>
+
+    <test> <!--Tested -->
+      <description>Testing removing cache paths</description>
+      <test-commands>
+        <cache-admin-command>-addPool pool1</cache-admin-command>
+        <cache-admin-command>-addDirective -path /foo -pool pool1</cache-admin-command>
+        <cache-admin-command>-addDirective -path /bar -pool pool1</cache-admin-command>
+        <cache-admin-command>-removePool pool1</cache-admin-command>
+        <cache-admin-command>-listDirectives -pool pool1</cache-admin-command>
+      </test-commands>
+      <cleanup-commands>
+      </cleanup-commands>
+      <comparators>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>Found 0 entries</expected-output>
+        </comparator>
+      </comparators>
+    </test>
+
+    <test> <!--Tested -->
+      <description>Testing listing directives filtered by pool</description>
+      <test-commands>
+        <cache-admin-command>-addPool pool1</cache-admin-command>
+        <cache-admin-command>-addPool pool2</cache-admin-command>
+        <cache-admin-command>-addDirective -path /foo -pool pool1</cache-admin-command>
+        <cache-admin-command>-addDirective -path /bar -pool pool1</cache-admin-command>
+        <cache-admin-command>-addDirective -path /baz -pool pool2</cache-admin-command>
+        <cache-admin-command>-addDirective -path /buz -pool pool2</cache-admin-command>
+        <cache-admin-command>-listDirectives -pool pool2</cache-admin-command>
+      </test-commands>
+      <cleanup-commands>
+        <cache-admin-command>-removePool pool1</cache-admin-command>
+        <cache-admin-command>-removePool pool2</cache-admin-command>
+      </cleanup-commands>
+      <comparators>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>Found 2 entries</expected-output>
+        </comparator>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>8   pool2  /baz</expected-output>
+        </comparator>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>9   pool2  /buz</expected-output>
+        </comparator>
+      </comparators>
+    </test>
+
+    <test> <!--Tested -->
+      <description>Testing listing directives filtered by path</description>
+      <test-commands>
+        <cache-admin-command>-addPool pool1</cache-admin-command>
+        <cache-admin-command>-addPool pool2</cache-admin-command>
+        <cache-admin-command>-addDirective -path /foo -pool pool1</cache-admin-command>
+        <cache-admin-command>-addDirective -path /bar -pool pool1</cache-admin-command>
+        <cache-admin-command>-addDirective -path /foo -pool pool2</cache-admin-command>
+        <cache-admin-command>-addDirective -path /bar -pool pool2</cache-admin-command>
+        <cache-admin-command>-listDirectives -path /foo</cache-admin-command>
+      </test-commands>
+      <cleanup-commands>
+        <cache-admin-command>-removePool pool1</cache-admin-command>
+        <cache-admin-command>-removePool pool2</cache-admin-command>
+      </cleanup-commands>
+      <comparators>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>Found 2 entries</expected-output>
+        </comparator>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>10  pool1  /foo</expected-output>
+        </comparator>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>12  pool2  /foo</expected-output>
+        </comparator>
+      </comparators>
+    </test>
+
+    <test> <!--Tested -->
+      <description>Testing listing directives filtered by path and pool</description>
+      <test-commands>
+        <cache-admin-command>-addPool pool1</cache-admin-command>
+        <cache-admin-command>-addPool pool2</cache-admin-command>
+        <cache-admin-command>-addDirective -path /foo -pool pool1</cache-admin-command>
+        <cache-admin-command>-addDirective -path /bar -pool pool1</cache-admin-command>
+        <cache-admin-command>-addDirective -path /foo -pool pool2</cache-admin-command>
+        <cache-admin-command>-addDirective -path /bar -pool pool2</cache-admin-command>
+        <cache-admin-command>-listDirectives -path /foo -pool pool2</cache-admin-command>
+      </test-commands>
+      <cleanup-commands>
+        <cache-admin-command>-removePool pool1</cache-admin-command>
+        <cache-admin-command>-removePool pool2</cache-admin-command>
+      </cleanup-commands>
+      <comparators>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>Found 1 entry</expected-output>
+        </comparator>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>16  pool2  /foo</expected-output>
+        </comparator>
+      </comparators>
+    </test>
+
+    <test> <!--Tested -->
+      <description>Testing removing a directive</description>
+      <test-commands>
+        <cache-admin-command>-addPool pool1</cache-admin-command>
+        <cache-admin-command>-addDirective -path /foo -pool pool1</cache-admin-command>
+        <cache-admin-command>-addDirective -path /bar -pool pool1</cache-admin-command>
+        <cache-admin-command>-removeDirective 18</cache-admin-command>
+        <cache-admin-command>-listDirectives</cache-admin-command>
+      </test-commands>
+      <cleanup-commands>
+        <cache-admin-command>-removePool pool1</cache-admin-command>
+      </cleanup-commands>
+      <comparators>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>Found 1 entry</expected-output>
+        </comparator>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>19  pool1  /bar</expected-output>
+        </comparator>
+      </comparators>
+    </test>
+
+    <test> <!--Tested -->
+      <description>Testing removing every directive for a path</description>
+      <test-commands>
+        <cache-admin-command>-addPool pool1</cache-admin-command>
+        <cache-admin-command>-addPool pool2</cache-admin-command>
+        <cache-admin-command>-addDirective -path /foo -pool pool1</cache-admin-command>
+        <cache-admin-command>-addDirective -path /foo -pool pool1</cache-admin-command>
+        <cache-admin-command>-addDirective -path /bar -pool pool1</cache-admin-command>
+        <cache-admin-command>-addDirective -path /foo -pool pool2</cache-admin-command>
+        <cache-admin-command>-addDirective -path /bar -pool pool2</cache-admin-command>
+        <cache-admin-command>-removeDirectives -path /foo</cache-admin-command>
+        <cache-admin-command>-listDirectives</cache-admin-command>
+      </test-commands>
+      <cleanup-commands>
+        <cache-admin-command>-removePool pool1</cache-admin-command>
+        <cache-admin-command>-removePool pool2</cache-admin-command>
+      </cleanup-commands>
+      <comparators>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>Found 2 entries</expected-output>
+        </comparator>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>22  pool1  /bar</expected-output>
+        </comparator>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>24  pool2  /bar</expected-output>
+        </comparator>
+      </comparators>
+    </test>
+
+  </tests>
+</configuration>
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/resources/testHDFSConf.xml b/hadoop-hdfs-project/hadoop-hdfs/src/test/resources/testHDFSConf.xml
index 00730da..248d06f 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/resources/testHDFSConf.xml
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/resources/testHDFSConf.xml
@@ -16524,7 +16524,7 @@
       </comparators>
     </test>
   
-  <test> <!--Tested -->
+    <test> <!--Tested -->
       <description>Verifying clrSpaceQuota operation is not permitted in safemode</description>
       <test-commands>
         <command>-fs NAMENODE -mkdir /test </command>