Whats new in version 0.90.6:INCOMPATIBLE CHANGES:
• HBASE-5228 [REST] Rip out "transform" feature
BUG FIXES:
• HBASE-5008 The clusters can't provide services because Region can't flush (Gaojinchao)
• HBASE-5020 MetaReader#fullScan doesn't stop scanning when vistor returns false in 0.90 version (Chunhui Shen)
• HBASE-4893 HConnectionImplementation is closed but not deleted (Mubarak)
• HBASE-4970 Add a parameter so that keepAliveTime of Htable thread pool can be changed (gaojinchao)
• HBASE-5060 HBase client is blocked forever (Jinchao)
• HBASE-5073 Registered listeners not getting removed leading to memory leak in HBaseAdmin (Ramkrishna)
• HBASE-5009 Failure of creating split dir if it already exists prevents splits from happening further
• HBASE-5041 Major compaction on non existing table does not throw error (Shrijeet)
• HBASE-5088 A concurrency issue on SoftValueSortedMap (Jieshan Bean and Lars H)
• HBASE-5156 Backport HBASE-4899 - Region would be assigned twice easily with continually killing server and moving region ...
Publisher review:Apache HBase™ is the Hadoop database, a distributed, scalable, big data store. Apache HBase is an open-source, distributed, versioned, column-oriented store modeled after Google's Bigtable: A Distributed Storage System for Structured Data by Chang et al. Just as Bigtable leverages the distributed data storage provided by the Google File System, Apache HBase provides Bigtable-like capabilities on top of Hadoop and HDFS. You can use Apache HBase when you need random, realtime read/write access to your Big Data.
Requirements:Operating system:Mac OS X
Apache HBase 0.90.6 details 
