http://hadoop.apache.org/common/docs/current/hdfs-default.html
http://hadoop.apache.org/common/docs/current/core-default.html
http://hadoop.apache.org/common/docs/current/mapred-default.html
http://wiki.apache.org/hadoop/HowManyMapsAndReduces
新旧版本配置名对比:
总入口
http://hadoop.apache.org/common/docs/current/
http://hadoop.apache.org/common/docs/current/hadoop-project-dist/hadoop-common/core-default.xml
http://hadoop.apache.org/common/docs/current/hadoop-project-dist/hadoop-hdfs/hdfs-default.xml