On Thu, Apr 20, 2017 at 2:31 AM, mj <li...@merit.unu.edu> wrote: > Hi Gregory, > > Reading your reply with great interest, thanks. > > Can you confirm my understanding now: > > - live snapshots are more expensive for the cluster as a whole, than taking > the snapshot when the VM is switched off?
No, it doesn't matter when the snapshot is taken. Just, once you take a snapshot, subsequent writes to any object in the snapshot (ie, every object in the RBD volume) will incur a copy. > > - using fstrim in VMs is (much?) more expensive when the VM has existing > snapshots? Hmm, I hadn't considered this one. Maybe? > > - it might be worthwhile to postpone upgrading from hammer to jewel, until > after your big accouncement? "Big announcement" is a bit much — several tunables will be restored in the next (10.2.8?) release. > - we are on xfs (both for the ceph OSDs and the VMs) and that is the best > combination to avoid these slow requests and CoW overhead with snapshots (or > at least to minimise their impact) > > Any other tips, do's or don'ts, or things to keep in mind related to > snapshots, VM/OSD filesystems, or using fstrim..? > > (our cluster is also small, hammer, three servers with 8 OSDs each, and > journals on ssd, plenty of cpu/ram) > > Again, thanks for your interesting post. > > MJ > > _______________________________________________ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
