The idea to use SSD/Flash as a cache is not new, and there are different solutions for this, both OpenSource like L2ARC for ZFS and Flashcache from Facebook, and proprietary, like directCache from Fusion-io.
They all however have some limitations, that’s why I am considering to have L2 cache on a database level, as an extension to InnoDB buffer pool.
Fortunately, there is a project in progress Flash_Cache_For_InnoDB by David which implements this.
David helped us to port his work to the latest Percona Server and you can get it from our launchpad Percona Server 5.5.28
I think that naming this as Flash_Cache is confusing due similarity to Flashcache from Facebook, so I prefer to name it as L2cache.
There is a quick benchmark on tpcc-mysql 2500W (250GB), I used
As we see the result is quite good an promising, so I am going to continue to research on further integration with Percona Server.
Right now there are two challenging questions, which we need to resolve: