Have you looked at Project Voldemort? http://project-voldemort.com/ http://project-voldemort.com/ Voldemort combines in memory caching with the storage system

Have you looked at Project Voldemort? http://project-voldemort.com/ http://project-voldemort.com/ Voldemort combines in memory caching with the storage system so that a separete caching tier is not required (instead the storage system itself is just fast.)