http://code.google.com/p/redis/

Redis 2.0.0 Stable is out!, Redis 2.0 is a major new version of Redis, with tons of new features, more speed, new data types, and less memory used. You can find a raw list of what is new reading the <U>Redis 2.0.0 Changelog page</U>.

Redis is an advanced key-value store. It is similar to memcached but the dataset is not volatile, and values can be strings, exactly like in memcached, but also lists, sets, and ordered sets. All this data types can be manipulated with atomic operations to push/pop elements, add/remove elements, perform server side union, intersection, difference between sets, and so forth. Redis supports different kind of sorting abilities.

In order to be very fast but at the same time persistent the whole dataset is taken in memory, and from time to time saved on disc asynchronously (semi persistent mode) or alternatively every change is written into an <U>append only file</U> (fully persistent mode). Redis is able to rebuild the append only file in background when it gets too big.

Redis supports <U>trivial to setup master-slave replication</U>, with very fast non-blocking first synchronization, auto reconnection on net split, and so forth.

Redis is written in ANSI C and works in most POSIX systems like Linux, <TT>*</TT>BSD, Mac OS X, Solaris, and so on. Redis is free software released under the very liberal BSD license. Redis is reported to compile and work under WIN32 if compiled with Cygwin, but there is no official support for Windows currently.