Cassandra

Apache Cassandra is an open source distributed database management system. It is an Apache Software Foundation top-level project[1] designed to handle very large amounts of data spread out across many commodity servers while providing a highly available service with no single point of failure. It is a NoSQL solution that was initially developed by Facebook and powered their Inbox Search feature until late 2010.[2][3] Jeff Hammerbacher, who led the Facebook Data team at the time, has described Cassandra as a BigTable data model running on an Amazon Dynamo-like infrastructure.[4] Cassandra provides a structured Key-Value store with tunable consistency. http://en.wikipedia.org/wiki/Apache_Cassandra