HBase vs. Cassandra: NoSQL Battle!
Two databases have garnered the most attention: HBase and Cassandra. The split between these equally ambitious projects can be categorized into Features (things missing that could be added any at time), and Architecture (fundamental differences that can’t be coded away). HBase is a near-clone of Google’s BigTable, whereas Cassandra purports to being a “BigTable/Dynamo hybrid”.
via: http://www.roadtofailure.com/2009/10/29/hbase-vs-cassandra-nosql-battle/