[Openstack] Live snapshot on Kilo - when/how?

Antonio Messina antonio.s.messina at gmail.com
Sun Nov 8 21:42:38 UTC 2015

Dear all,

I noticed that live snapshots are disabled (since juno at least) when
using "rbd" or "lvm" storage, even when
workarounds.disable_libvirt_snapshots is False

The culprit is https://github.com/openstack/nova/blob/master/nova/virt/libvirt/driver.py#L1374

but I don't understand why: the comment only mentions encrypted
ephemeral LVM storage, and then also says that LVM requires cold
snapshot anyway, but there is no mention of any issue/mailing list
thread. At the same time, no mention of ceph is present.

So: is it dangerous/unsupported? Why? Why also ceph is unsupported?

I'm using RBD for ephemeral storage, using a patch to implement nova
snapshots using ceph layering, and our compute nodes have very little
disk space, which means that it's very likely that snapshots will fail
because libvirt is unable to save the ram state to disk.

Thank you in advance,
Antonio messina

antonio.s.messina at gmail.com
antonio.messina at uzh.ch                     +41 (0)44 635 42 22
S3IT: Service and Support for Science IT   http://www.s3it.uzh.ch/
University of Zurich
Winterthurerstrasse 190
CH-8057 Zurich Switzerland

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