Bcache: Caching beyond just RAM [LWN.net]

Bcache: Caching beyond just RAM

Posted Jul 8, 2010 3:35 UTC (Thu) by dlang (guest, #313)
In reply to: Bcache: Caching beyond just RAM by koverstreet
Parent article: Bcache: Caching beyond just RAM

a local magnetic drive may be faster than a network drive

to post comments

Bcache: Caching beyond just RAM

Posted Jul 8, 2010 11:13 UTC (Thu) by ewan (guest, #5533) [Link] (1 responses)

And a small fast disk system (e.g. striped 15k SAS disks) may be a useful cache over a big slow one (e.g. a huge RAID of 5400rpm SATA disks).

I wonder if bcache can be stacked? So you could have an SSD over some SAS disks over a SATA RAID?

Bcache: Caching beyond just RAM

Posted Jul 8, 2010 11:24 UTC (Thu) by koverstreet (✭ supporter ✭, #4296) [Link]

There's no way to do that now - all the cache devices in the system are pooled together and used symmetrically - but it is something I've been considering down the road. It might not be all that much more work, I'm just curious if the performance would justify it. Most people's working set just isn't all that huge, and also the big problem with your big slow raid6 is random writes, which bcache should be able to mostly eliminate. But we'll see.