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Apache Hadoop ${project.version}
================================

Apache Hadoop ${project.version} is a minor release in the 2.x.y release
line, building upon the previous stable release 2.9.2.

Here is a short overview of the major features and improvements.

*   HDFS

    *   Consistent reads from standby node. This allows better load balancing on HDFS
        clusters, especially those with a high read/write operation ratio. See
        [HDFS-12943](https://jira.apache.org/jira/browse/HDFS-12943) and
        [HDFS-14204](https://jira.apache.org/jira/browse/HDFS-14204) for more details.

    *   Improvements related to rolling upgrade support from 2.x to 3.x.

    *   NameNode port based selective encryption. This allows enforcing different security
        constraints for different types of traffic. See [HDFS-13541](https://issues.apache.org/jira/browse/HDFS-13541)
        for more details.

    *   Cost-based fair call queue. This improves fairness and stability in a large, multi-tenant
        HDFS cluster. See [HDFS-14403](https://issues.apache.org/jira/browse/HDFS-14403) for more details.

*   YARN

    *   Support for user-defined countable resource types beyond CPU and memory. This was
        ported from the 3.x.y release line. See [YARN-3926](https://issues.apache.org/jira/browse/YARN-3926),
        [YARN-8200](https://issues.apache.org/jira/browse/YARN-8200),
        and the [YARN resource model documentation](./hadoop-yarn/hadoop-yarn-site/ResourceProfiles.html) for
        more information.

    *   Native support for GPUs as a schedulable resource type. This builds on the above, and was also ported
        from the 3.x.y release line. See [YARN-6223](https://issues.apache.org/jira/browse/YARN-6223) and
        [YARN-8200](https://issues.apache.org/jira/browse/YARN-8200) for more information.

Getting Started
===============

The Hadoop documentation includes the information you need to get started using
Hadoop. Begin with the
[Single Node Setup](./hadoop-project-dist/hadoop-common/SingleCluster.html) which
shows you how to set up a single-node Hadoop installation. Then move on to the
[Cluster Setup](./hadoop-project-dist/hadoop-common/ClusterSetup.html) to learn how
to set up a multi-node Hadoop installation.