Re: [ceph-users] Snapshots and fstrim with cache tiers ?
Hello, The snapshot with a cache tier part was answered by Greg Farnum (https://www.mail-archive.com/ceph-users@lists.ceph.com/msg18329.html). What about fstrim with a cache tier ? It doesn't seem to work. Also is there a background task that recovers freed blocks ? Best regards, Frédéric. Le 25/03/2015 11:14, Frédéric Nass a écrit : Hello, I have a few questions regarding snapshots and fstrim with cache tiers. In the cache tier and erasure coding FAQ related to ICE 1.2 (based on Firefly), Inktank says Snapshots are not supported in conjunction with cache tiers. What are the risks of using snapshots with cache tiers ? Would this better not use it recommandation still be true with Giant or Hammer ? Regarding the fstrim command, it doesn't seem to work with cache tiers. The freed up blocks don't get back in the ceph cluster. Can someone confirm this ? Is there something we can do to get those freed up blocks back in the cluster ? Also, can we run an fstrim task from the cluster side ? That is, without having to map and mount each rbd image or rely on the client to operate this task ? Best regards, -- Frédéric Nass Sous-direction Infrastructures Direction du Numérique Université de Lorraine email : frederic.n...@univ-lorraine.fr Tél : +33 3 83 68 53 83 ___ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com -- Frédéric Nass Sous direction des Infrastructures, Direction du Numérique, Université de Lorraine. Tél : 03.83.68.53.83 ___ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
Re: [ceph-users] Snapshots and fstrim with cache tiers ?
On Wed, Mar 25, 2015 at 3:14 AM, Frédéric Nass frederic.n...@univ-lorraine.fr wrote: Hello, I have a few questions regarding snapshots and fstrim with cache tiers. In the cache tier and erasure coding FAQ related to ICE 1.2 (based on Firefly), Inktank says Snapshots are not supported in conjunction with cache tiers. What are the risks of using snapshots with cache tiers ? Would this better not use it recommandation still be true with Giant or Hammer ? Regarding the fstrim command, it doesn't seem to work with cache tiers. The freed up blocks don't get back in the ceph cluster. Can someone confirm this ? Is there something we can do to get those freed up blocks back in the cluster ? It does work, but there are two effects you're missing here: 1) The object can be deleted in the cache tier, but it won't get deleted from the backing pool until it gets flushed out of the cache pool. Depending on your workload this can take a while. 2) On erasure-coded pool, the OSD makes sure it can roll back a certain number of operations per PG. In the case of deletions, this means keeping the object data around for a while. This can also take a while if you're not doing many operations. This has been discussed on the list before; I think you'll want to look for a thread about rollback and pg log size. -Greg Also, can we run an fstrim task from the cluster side ? That is, without having to map and mount each rbd image or rely on the client to operate this task ? Best regards, -- Frédéric Nass Sous-direction Infrastructures Direction du Numérique Université de Lorraine email : frederic.n...@univ-lorraine.fr Tél : +33 3 83 68 53 83 ___ 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
[ceph-users] Snapshots and fstrim with cache tiers ?
Hello, I have a few questions regarding snapshots and fstrim with cache tiers. In the cache tier and erasure coding FAQ related to ICE 1.2 (based on Firefly), Inktank says Snapshots are not supported in conjunction with cache tiers. What are the risks of using snapshots with cache tiers ? Would this better not use it recommandation still be true with Giant or Hammer ? Regarding the fstrim command, it doesn't seem to work with cache tiers. The freed up blocks don't get back in the ceph cluster. Can someone confirm this ? Is there something we can do to get those freed up blocks back in the cluster ? Also, can we run an fstrim task from the cluster side ? That is, without having to map and mount each rbd image or rely on the client to operate this task ? Best regards, -- Frédéric Nass Sous-direction Infrastructures Direction du Numérique Université de Lorraine email : frederic.n...@univ-lorraine.fr Tél : +33 3 83 68 53 83 ___ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
