On Fri, 07 Feb 2014 18:46:31 +0100 Christian Kauhaus wrote: > Am 07.02.2014 14:42, schrieb Mark Nelson: > > Ok, so the reason I was wondering about the use case is if you were > > doing RBD specifically. Fragmentation has been something we've > > periodically kind of battled with but still see in some cases. BTRFS > > especially can get pretty spectacularly fragmented due to COW and > > overwrites. There's a thread from a couple of weeks ago called "rados > > io hints" that you may want to look at/contribute to. > > Thank you for the hint. Sage's proposal on ceph-devel sounds good, so > I'll wait for an implementation. > Pardon me for stating the maybe painfully obvious, but wouldn't setting the allocsize to 4MB (with XFS and the default Ceph object size) do a world of good to prevent fragmentation? Nothing like tjat in ext4, though dealloc might help. Despite really liking btrfs a lot it consistently comes in last by quite a margin when it comes to speed, especially in my main use case of mail storage (the clear winner there is ext4, followed by XFS). And the KVM people warn against using it as a backing store for a reason. ^.^ Regards, Christian (another one) -- Christian Balzer Network/Systems Engineer chibi@xxxxxxx Global OnLine Japan/Fusion Communications http://www.gol.com/ _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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