记录
UML
http://cloud.ozyegin.edu.tr/Hadoop-UML-Diagrams/Documentation/html/d2/d77/namespaceorg_1_1apache_1_1hadoop_1_1hdfs.html
java code: TestUtil
http://grepcode.com/file/repository.cloudera.com/content/repositories/releases/org.apache.hadoop/hadoop-test/0.20.2-cdh3u1/org/apache/hadoop/hdfs/DFSTestUtil.java#DFSTestUtil
HDFS API
http://hadoop.apache.org/hdfs/docs/r0.21.0/api/index.html
http://hadoop.apache.org/hdfs/docs/current/api/index.html
HADOOP API
http://hadoop.apache.org/common/docs/current/api/