在路上，一个不经意，发现hadoop.apache.org上"Release 2.2.0 available，Apache Hadoop 2.2.0 is the GA release of Apache Hadoop 2.x"了，上次看到Beta版本发布恍惚好像是在昨天，不到两个月这才，好快！是为了配合月底的Hadoop World吗 :=) 这第四季度才过去一丁点，想必业界会有更多精彩回应。。。

Apache Hadoop 2.2.0发布新闻摘要转载：

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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.

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对于广大Cloudera CDH用户而言，不少Hadoop 2里的新特性其实早已经被包含在CDH的最新版本里，譬如HDFS HA, network encryption等，也就是说大家已经早早在享受Hadoop 2的这些新特性了。迫不及待想要全面升级？稍安勿躁，下一个版本CDH5将完全基于Hadoop 2。。。

ITPub博客

Apache Hadoop真的“二”了这回