> Von: Stefan Wendler [stefan.wend...@tngtech.com] > Gesendet: Montag, 27. Oktober 2014 11:39 > An: Markus Stockhausen > Cc: users@ovirt.org > Betreff: Re: [ovirt-users] Deleting large snapshots blocks the whole cluster > > Hi, > > do you mean during snapshot deletion or in general? > > In general we do not have any swap usage at all. On none of the 4 hosts. > > We had some swap I/O on the host that is SPM most of the time. But not > during that period where we tried to delete the snapshot. >
I thought of the bug described in RH bugzilla 1138690 "[SCALE] snapshot deletion -> heavy swapping on SPM". In case you have no access to it (as it is RHEV tagged): qemu-img reads through pagecache during snapshot deletion. A new flag has been intrduced in August this year that allows to avoid page cache. This flag must be provided by OVirt/RHEV. Target release is 3.6. Until then the only bugfix is to drop pagecache manually on regular intervals on the hypversior and especially the SPM node. Markus > > Cheers, > Stefan > > On 10/27/14 11:08, Markus Stockhausen wrote: > > Do you see swapping on the SPM? If yes a regular echo 3 > drop_caches could > > help. > > > > Markus > > > > Am 27.10.2014 10:57 schrieb Stefan Wendler <stefan.wend...@tngtech.com>: > > Hi, > > > > we have some really large snapshots left from a migration. Since our > > store is almost full now we have to delete them now. > > > > Some snapshots are around 1TB already. > > > > The last time we tried to delete a ~500GB snapshot the delete task > blocked the whole diskstore's IO and the whole cluster and all hosts > became unavailable. > > Is there a way to delete large snapshots in a "humane" way that will not > block everything? > > Cheers, > Stefan > >
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