[nemilar]

Not to spam, but hopefully this information is useful for some HN'ers. Our startup, http://velobit.com, provides caching as well.

Alas, it is not open source, but it does have some differentiators over bcache/dm-cache. The primary pro's of those two are that they are FOSS.

Major downsides are they they are kernel patches. DM-Cache is a little more difficult as well, in the sense that it is in the DM layer, so you're creating a new device when you apply caching. Contrast with our startup, where we insert ourselves directly into the existing devices (so no need to modify fstab, etc..). Of course, I like to think we have other major differentiators as well, but I won't go on and on about them here..

That being said, this caching (especially SSD-as-caching) space is huge right now, even though it doesn't get much attention in the hot-tech startup world.

[nwmcsween]

There's also hot tracking RFC patches floating around for the VFS layer. bcache seems quiet nice, there are block layer refactorings going on right now in order to get it merged.