Ryan King gave a good summary in his interview. (http://nosql.mypopescu.com/post/407159447/cassandra-twitter-an-interview-with-ryan-king http://nosql.mypopescu

Ryan King gave a good summary in his interview. (http://nosql.mypopescu.com/post/407159447/cassandra-twitter-an-interview-with-ryan-king http://nosql.mypopescu.com/post/407159447/cassandra-twitter-...) Basically, Cassandra has the best answers to the important questions: How will we add new machines? Are their any single points of failure? Do the writes scale as well? How much administration will the system require? If its open source, is there a healthy community? (And I would add, is it _fast_ as well as scalable?)