hadoop2.2.0稳定版本发布了

        期待已久的HADOOP2.2.0稳定版本终于在2013年10月15号发布了，由于hadoop1.0时代出现了诸多的问题，在2.0将解决大部分问题，并且这是必然趋势，相信2.0时代将会很快替代1.0时代。以下是从官方网站摘取的主要Release Notes，详细请看官方说明。

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.
比较有趣的是，上面有一个比较大的改变，那就是可以支持运行在windows平台。并且我下载源码后编译成64bit，安装在centos上测试了下，速度明显提升不少，让我很兴奋，另外在yarn-site.xml配置文件中，yarn.nodemanager.aux-services属性的值由原来的mapreduce.shuffle改为mapreduce_shuffle需要注意的地方，不然运行自带wordcount例子报错，由于时间关系，写的比较随意，以后有时间会详细写些教程。

<property>
<name>yarn.nodemanager.aux-services</name>
<value>mapreduce_shuffle</value>
<description>shuffle service that needs to be set for Map Reduce to run </description>
</property>