Membase.org
http://www.membase.org/

For those familiar with memcached, membase provides on-the-wire protocol compatibility, but adds disk persistence; hierarchical storage management; data replication; live cluster reconfiguration and rebalancing; and secure multi-tenancy with data partitioning. Like memcached, membase is simple, fast and elastic.

Persistent Key/Value Storage

Membase is an open-source (Apache 2.0 license) distributed, key-value database management system optimized for storing data behind interactive web applications. These applications must service many concurrent users; creating, storing, retrieving, aggregating, manipulating and presenting data in real-time. Supporting these requirements, membase processes data operations with quasi-deterministic low latency and high sustained throughput.

from oreilly news link

Membase is an open-source (Apache 2.0 license) distributed, key-value database management system optimized for storing data behind interactive web applications. These applications must service many concurrent users; creating, storing, retrieving, aggregating, manipulating and presenting data in real-time. Supporting these requirements, membase processes data operations with quasi-deterministic low latency and high sustained throughput. It scales linearly from a single-server deployment to a cluster of thousands of machines. And because membase does not require creation of a schema before storing data, it is a flexible, cost-effective place to Store Lots of Stuff.

Membase is an open-source (Apache 2.0 license) distributed, key-value database management system optimized for storing data behind interactive web applications. These applications must service many concurrent users; creating, storing, retrieving, aggregating, manipulating and presenting data in real-time. Supporting these requirements, membase processes data operations with quasi-deterministic low latency and high sustained throughput. It scales linearly from a single-server deployment to a cluster of thousands of machines. And because membase does not require creation of a schema before storing data, it is a flexible, cost-effective place to Store Lots of Stuff. The original membase source code was released as Open Source by NorthScale, Zynga and NHN to membase.org in June 2010.