Hadoop is based on Apache Hadoop 2.4 and includes the following additional patches:
HDFS-5257: addBlock() retry should return LocatedBlock with locations else client will get AIOBE
HDFS-5089: When a LayoutVersion supports SNAPSHOT, it must support
FSIMAGE_NAME_OPTIMIZATION.HADOOP-10475: ConcurrentModificationException in AbstractDelegationTokenSelector.selectToken().
HDFS-6160: TestSafeMode occasionally fails.
HDFS-6233: Datanode throws HardLink exception during upgrade from 1.3 to 2.1 in Windows.
