On 09/14/2014 05:11 PM, Andrei Mikhailovsky wrote:
Hello guys,
Was wondering if anyone uses or done some testing with using bcache or
enhanceio caching in front of ceph osds?
I've got a small cluster of 2 osd servers, 16 osds in total and 4 ssds
for journals. I've recently purchased four additional ssds to be used
for ceph cache pool, but i've found performance of guest vms to be
slower with the cache pool for many benchmarks. The write performance
has slightly improved, but the read performance has suffered a lot (as
much as 60% in some tests).
Therefore, I am planning to scrap the cache pool (at least until it
matures) and use either bcache or enhanceio instead.
We're actually looking at dm-cache a bit right now. (and talking some of
the developers about the challenges they are facing to help improve our
own cache tiering) No meaningful benchmarks of dm-cache yet though.
Bcache, enhanceio, and flashcache all look interesting too. Regarding
the cache pool: we've got a couple of ideas that should help improve
performance, especially for reads. There are definitely advantages to
keeping cache local to the node though. I think some form of local node
caching could be pretty useful going forward.
Thanks
Andrei
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