Apache Hadoop 2 穩定版釋出

15 October, 2013: Release 2.2.0 available
最大的亮點在於引入了YARN，並且提升了 HDFS的可用性及其他所需的特性。

YARN 在 HDFS 之上，作為一個服務於大資料應用的大規模、分散式作業系統，允許多個應用程式在其整個生命週期同時執行，以更加高效地支援資料。
Hadoop 2 和 YARN 使使用者能夠混合批次、互動和實時的工作負載在一個穩定的 Hadoop 生態系統的基礎部分。

Apache Hadoop 2.2.0 is the GA release of Apache Hadoop 2.x.

Users are encouraged to immediately move to 2.2.0 since this release is significantly more stable and is guaranteed to remain compatible in terms of both APIs and protocols.

To recap, this release has a number of significant highlights compared to Hadoop 1.x:

    YARN - A general purpose resource management system for Hadoop to allow MapReduce and other other data processing frameworks and services
    High Availability for HDFS
    HDFS Federation
    HDFS Snapshots
    NFSv3 access to data in HDFS
    Support for running Hadoop on Microsoft Windows
    Binary Compatibility for MapReduce applications built on hadoop-1.x
    Substantial amount of integration testing with rest of projects in the ecosystem

A couple of important points to note while upgrading to hadoop-2.2.0:

    HDFS - The HDFS community decided to push the symlinks feature out to a future 2.3.0 release and is currently disabled.
    YARN/MapReduce - Users need to change ShuffleHandler service name from mapreduce.shuffle to mapreduce_shuffle.

Please see the Hadoop 2.2.0 Release Notes for details.

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