[ovirt-users] Snapshot removal time

[Ala Hino]

Hello,

What's the version of the manager (engine)?

Could you please provide the link or the SPM and the host running the VM?

Thanks,
Ala

On Sep 22, 2017 1:19 PM, "Troels Arvin" <troels at arvin.dk> wrote:

> Hello,
>
> I have a RHV 4.1 virtualized guest-server with a number of rather large
> VirtIO virtual disks attached. The virtual disks are allocated from a
> fibre channel (block) storage domain. The hypervisor servers run RHEL 7.4.
>
> When I take a snapshot of the guest, then it takes a long time to remove
> the snapshots again, when the guest is powered off (a snapshot of a 2 TiB
> disk takes around 3 hours to remove). However, when the guest is running,
> then snapshot removal is very quick (perhaps around five minutes per
> snapshot). The involved disks have not been written much to while they
> had snapshots.
>
> I would expect the opposite: I.e., when the guest is turned off, then I
> would assume that oVirt can handle snapshot removal in a much more
> aggressive fashion than when performing a live snapshot removal?
>
> When performing offline snapshot removal, then on the hypervisor having
> the SPM role, I see the following in output from "ps xauw":
>
> vdsm 10255 8.3 0.0 389144 27196 ? S<l 13:40 7:04 /usr/bin/qemu-img
> convert -p -t none -T none -f qcow2 /rhev/data-center/mnt/blockSD/xxx/
> images/yyy/zzz -O raw /rhev/data-center/mnt/blockSD/xxx/images/yyy/
> zzz_MERGE
>
> I don't see the same kind of process running on a guest's hypervisor when
> online snapshot removal is in progress.
>
> I've read most of https://www.ovirt.org/develop/release-management/
> features/storage/remove-snapshot/
> My interpretation from that document is that I should expect to see "qemu-
> img commit" commands instead of "qemu-img convert" processes. Or?
>
> The RHV system involved is somewhat old, having been upgrade many times
> from 3.x through 4.1. Could it be that it carries around old left-overs
> which results in obsolete snapshot removal behavior?
>
> --
> Regards,
> Troels Arvin
>
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