Hi, Le 13/04/2017 à 10:51, Peter Maloney a écrit : > [...] > Also more things to consider... > > Ceph snapshots reaaaally slow things down. We use rbd snapshots on Firefly (and Hammer now) and I didn't see any measurable impact on performance... until we tried to remove them. We usually have at least one snapshot per VM image, often 3 or 4. Note that we use BTRFS filestores where IIRC the CoW is handled by the filesystem so it might be faster compared to the default/recommended XFS filestores. > They aren't efficient like on > zfs and btrfs. Having one might take away some % performance, and having > 2 snaps takes potentially double, etc. until it is crawling. And it's > not just the CoW... even just rbd snap rm, rbd diff, etc. starts to take > many times longer. See http://tracker.ceph.com/issues/10823 for > explanation of CoW. My goal is just to keep max 1 long term snapshot.[...] In my experience with BTRFS filestores, snap rm impact is proportional to the amount of data specific to the snapshot being removed (ie: not present on any other snapshot) but completely unrelated to the number of existing snapshots. For example the first one removed can be handled very fast and it can be the last one removed that takes the most time and impacts the most the performance. Best regards, Lionel _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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