linux - Using SSD as disk cache

Is there software for Linux to use an SSD as disk cache? I believe that Sun does something like this with ZFS, though not sure. A quick search provides nothing suitable. The goal would be to put frequently requested files on the SSD on-the-fly. Since the SSD has more capacity than RAM for less money and better performance than hard disk, this should provide an efficient performance boost.

Answer

Facebook recently released a module for the Linux kernel called 'FlashCache' which can do exactly this:

http://github.com/facebook/flashcache