| // 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. |
| = Persistent Storage |
| |
| == Overview |
| |
| Apache Ignite Persistence is designed to provide a quick and responsive persistent storage. |
| When using the persistent storage, Ignite stores all the data on disk, and loads as much data as it can into RAM for processing. |
| |
| When persistence is enabled, Ignite stores each partition in a separate file on disk. In addition to data partitions, Ignite stores indexes and metadata. |
| |
| == Checkpointing |
| |
| _Checkpointing_ is the process of copying dirty pages from RAM to partition files on disk. A dirty page is a page that was updated in RAM but was not written to the respective partition file. |
| |
| After a checkpoint is created, all changes are persisted to disk and will be available if the node crashes and is restarted. |
| |
| Checkpointing is designed to ensure durability of data and recovery in case of a node failure. |
| |
| |
| This process helps to utilize disk space frugally by keeping pages in the most up-to-date state on disk. |
| |
| |
| == Configuration Properties |
| |
| The following table describes some properties of persistent data storage: |
| |
| [cols="1,1,3",opts="header", stripes=none] |
| |=== |
| |Property|Default|Description |
| |
| |name|| The name of the data region. |
| |size|`256 * 1024 * 1024`| Sets the space allocated to the data region, in bytes. |
| |replacementMode|`CLOCK`| Sets the page replacement algorithm. |
| |pageSize|16384| The size of pages in the storage, in bytes. |
| |memoryAllocator.type|unsafe|Memory allocator configuration. Uses `sun.misc.Unsafe` to improve performance. Currently, no other options are available. |
| |=== |
| |
| The table below describes checkpoint configuration: |
| |
| [cols="1,1,3",opts="header", stripes=none] |
| |=== |
| |Property|Default|Description |
| |checkpointDelayMillis|200| Delay before staring a checkpoint after receiving the command. |
| |checkpointThreads|4| Number of CPU threads dedicated to checkpointing. |
| |compactionThreads|4| Number of CPU threads dedicated to data compaction. |
| |frequency|180000|Checkpoint frequency in milliseconds. |
| |frequencyDeviation|40| Allowed deviation in checkpoint frequency, in milliseconds. |
| |logReadLockThresholdTimeout|0| Threshold for logging long read locks, in milliseconds. |
| |readLockTimeout|10000| Timeout for checkpoint read lock acquisition, in milliseconds. |
| |useAsyncFileIoFactory|true| If Ignite uses asynchronous file I/O operations provider. |
| |=== |
| |
| == Configuration Example |
| |
| The example below shows how to configure one data region that uses Ignite persistence: |
| |
| ---- |
| ignite config set --type cluster \ |
| "{ |
| aipersist.regions: [{ |
| name: btree_persistent_region, |
| maxSize: 256000000 |
| }] |
| }" |
| ---- |