Facebook released a kernel module called Flashcache this wednesday, which is used to speed up MySQL by caching data in faster media like SSD disks. It’s only tested for kernel versions 2.6.18 and 2.6.20.
As mentioned at Facebook.com:
We built Flashcache to help us scale InnoDB/MySQL, but it was designed as a generic caching module that can be used with any application built on top of any block device. For InnoDB, when the working set does not fit in the InnoDB buffer pool, read latency is significantly improved due to caching more of the working set in faster media, such as SSD’s. We also improve write performance by first caching writes in SSD’s and lazily flushing the data back to disk.
It looks like its based on the dm-cache work. It’s nice to see that moving again.