On Mon, Jul 11, 2016 at 04:53:36PM +0200, Lionel Bouton wrote: > Le 11/07/2016 11:56, Brad Hubbard a écrit : > > On Mon, Jul 11, 2016 at 7:18 PM, Lionel Bouton > > <lionel-subscription@xxxxxxxxxxx> wrote: > >> Le 11/07/2016 04:48, 한승진 a écrit : > >>> Hi cephers. > >>> > >>> I need your help for some issues. > >>> > >>> The ceph cluster version is Jewel(10.2.1), and the filesytem is btrfs. > >>> > >>> I run 1 Mon and 48 OSD in 4 Nodes(each node has 12 OSDs). > >>> > >>> I've experienced one of OSDs was killed himself. > >>> > >>> Always it issued suicide timeout message. > >> This is probably a fragmentation problem : typical rbd access patterns > >> cause heavy BTRFS fragmentation. > > To the extent that operations take over 120 seconds to complete? Really? > > Yes, really. I had these too. By default Ceph/RBD uses BTRFS in a very > aggressive way, rewriting data all over the place and creating/deleting > snapshots every filestore sync interval (5 seconds max by default IIRC). > > As I said there are 3 main causes of performance degradation : > - the snapshots, > - the journal in a standard copy-on-write file (move it out of the FS or > use NoCow), > - the weak auto defragmentation of BTRFS (autodefrag mount option). > > Each one of them is enough to impact or even destroy performance in the > long run. The 3 combined make BTRFS unusable by default. This is why > BTRFS is not recommended : if you want to use it you have to be prepared > for some (heavy) tuning. The first 2 points are easy to address, for the > last (which begins to be noticeable when you accumulate rewrites on your > data) I'm not aware of any other tool than the one we developed and > published on github (link provided in previous mail). > > Another thing : you better have a recent 4.1.x or 4.4.x kernel on your > OSDs if you use BTRFS. We've used it since 3.19.x but I wouldn't advise > it now and would recommend 4.4.x if it's possible for you and 4.1.x > otherwise. Thanks for the information. I wasn't aware things were that bad with BTRFS as I haven't had much to do with it up to this point. Cheers, Brad > > Best regards, > > Lionel -- Cheers, Brad _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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