hadoop提高性能建议
http://langyu.iteye.com/blog/916304
http://apps.hi.baidu.com/share/detail/31497615
hadoop中每个节点map和reduce个数的设置调优
http://samuschen.iteye.com/blog/859971
Job.setNumMapTasks
http://www.hadoopor.com/thread-1207-1-1.html
http://topic.csdn.net/u/20090407/19/418ed3df-7a80-4ad9-8e33-c2ca1b3350a9.html
Hadoop平台优化综述（一）
http://dongxicheng.org/mapreduce/hadoop-optimization-0/
