[one-dev] OpenNebula storage cache?

[Stuart Longland]

Hi all,

I've been doing a bit of work in getting a combined Ceph+FlashCache
driver going for OpenNebula.  At the moment I've got some initial
proof-of-concept code which is based on the current stable OpenNebula
release.  Things seem to be working but the testing has been light.

Some rationale behind the idea is here:
http://stuartl.longlandclan.yi.org/blog/2014/04/03/ceph-and-flashcache-in-opennebula/

There you'll also find a link to the git repository.

It got me thinking though.  Right now my cache and back-end drivers are
very tightly coupled.  How viable would it be, to have a "cache" driver,
much like we've got drivers for the actual datastores, and drivers for
moving data between datastores?

Right now my work has focussed on using Ceph RBDs and FlashCache
together.  I'm curious to try bcache, but that will require re-writing
chunks of code.  If someone wanted to use this driver with an iSCSI/CLVM
back-end, they're in for similar rewriting tasks.

A local cache is useful in any scenario where shared storage is accessed
over a network.

Are there any thoughts on how one might implement this?

Regards,
-- 
Stuart Longland
Systems Engineer
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