[cinder][nova] fsfreeze hooks issues with cinder snapshot/backup

Sofia Enriquez senrique at redhat.com
Tue Aug 31 15:19:54 UTC 2021


As far as I can see cinder hasn't implemented this. However, I'm not sure
about the status of this feature because the last update was on 2014[1]

I think it's important to mention that this would only affect the live
snapshots (handled by Nova) but for any other scenario every cinder driver
optimized the snapshot/backup creation in a different way.

This sounds like a good PTG discussion topic.  You can add it to the
planning etherpad here:

There's also info about the dates and times we'll be meeting on that



On Tue, Aug 31, 2021 at 11:52 AM Arthur Outhenin-Chalandre <
arthur.outhenin-chalandre at cern.ch> wrote:

> Hello,
> We are trying to trigger an fsfreeze via a cinder backup or snapshot. We
> confirmed that the fsfreeze hooks are actually called with a nova
> snapshot with `/var/log/qga-fsfreeze-hook.log` in the VM, but we can't
> achieve the same thing with a cinder backup/snapshot attached to the
> same instance. We are using Wallaby, libvirt, RBD for cinder volumes and
> RBD as well for cinder-backup.
> According to this (old) spec [0], cinder should call the `quiesce()`
> method in nova during backup/snapshot. We looked in the cinder code and
> couldn't find any clear evidence that this method is actually called by
> cinder (but we may have missed something). We added some debug messages
> on quiesce/can_quiesce/require_quiesce/... in
> `nova/virt/libvirt/driver.py` and they are never called with a cinder
> backup/snapshot in our setup while they are (and succeed) if we do a
> nova snapshot.
> We are starting to suspect that something is missing in cinder, but it
> could very well be a problem with our setup as well... Does someone use
> this feature or know if it should be working/implemented?
> [0]:
> https://wiki.openstack.org/wiki/Cinder/QuiescedSnapshotWithQemuGuestAgent#Cinder
> Cheers,
> --
> Arthur Outhenin-Chalandre


L. SofĂ­a Enriquez


Software Engineer

Red Hat PnT <https://www.redhat.com>

IRC: @enriquetaso
@RedHat <https://twitter.com/redhat>   Red Hat
<https://www.linkedin.com/company/red-hat>  Red Hat
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