Hello, On 8/31/21 5:19 PM, Sofia Enriquez wrote:

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]

Oh ok, I was hoping it was a setup problem on our side. Thanks for letting me know, it has saved me from further testing/research!

This sounds like a good PTG discussion topic.  You can add it to the planning etherpad here: https://etherpad.opendev.org/p/yoga-ptg-cinder-planning <https://etherpad.opendev.org/p/yoga-ptg-cinder-planning>

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

I added the discussion topic and I will be around to discuss it. I should be able to participate in the dev if needed as well. Cheers, -- Arthur Outhenin-Chalandre

On 8/31/2021 10:19 AM, Sofia Enriquez wrote:

Hello,

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 remember being a part of these discussions and the fact that there was interest in getting it working.  I am wondering if this was just a case where no one followed through on implementation. It might be that we encountered an unexpected challenge that I don't remember. Either way, I do agree that this would be a good topic for the PTG.

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: https://etherpad.opendev.org/p/yoga-ptg-cinder-planning <https://etherpad.opendev.org/p/yoga-ptg-cinder-planning>

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

Cheers, Sofia

[1] https://blueprints.launchpad.net/cinder/+spec/quiesced-snapshots-with-qemu-g... <https://blueprints.launchpad.net/cinder/+spec/quiesced-snapshots-with-qemu-guest-agent>

On Tue, Aug 31, 2021 at 11:52 AM Arthur Outhenin-Chalandre <arthur.outhenin-chalandre@cern.ch <mailto:arthur.outhenin-chalandre@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#Ci... <https://wiki.openstack.org/wiki/Cinder/QuiescedSnapshotWithQemuGuestAgent#Cinder>

Cheers,

-- Arthur Outhenin-Chalandre

--

L. Sofía Enriquez

she/her

Software Engineer

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

IRC: @enriquetaso

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