[Openstack] nova backup - instances unreachable

John Petrini jpetrini at coredial.com
Wed Jan 11 14:22:45 UTC 2017

Hi Eugen,

Thanks for the response! That makes a lost of sense and is what I figured
was going on but I missed it in the documentation. We use Ceph as well and
I had considered doing the snapshots at the RBD level but I was hoping
there was someway to accomplish this via nova. I came across this Sebastien
Han write-up that claims this functionality was added to Mitaka:

We are running Mitaka but our snapshots are not happening at the RBD level,
they are being copied and uploaded to glance which takes up a lot of space
and is very slow.

Have you or anyone else implemented this in Mitaka? Other than Sebastian's
blog I haven't found any documentation on this.

Thank You,


John Petrini

On Wed, Jan 11, 2017 at 3:32 AM, Eugen Block <eblock at nde.ag> wrote:

> Hi,
> this seems to be exptected, the docs say:
> "Shut down the source VM before you take the snapshot to ensure that all
> data is flushed to disk."
> So if the VM is not shut down, it's freezed to prevent data loss (I
> guess). Depending on your storage backend, there are other ways to perform
> backups of your VMs.
> We use Ceph as backend for nova, glance and cinder. Ceph stores the disks,
> images and volumes as Rados block device objects. We have a backup script
> that creates snapshots of these RBDs, which are exported to our backup
> drive. This way the running VM is not stopped or freezed, the user doesn't
> notice any issues. Unlike a nova snapshot, the rbd snapshot is created
> immediately within a few seconds. After a successful backup the snapshots
> are removed.
> Hope this helps! If you are interested in Ceph, visit [1].
> Regards,
> Eugen
> [1] http://docs.ceph.com/docs/giant/start/intro/
> Zitat von John Petrini <jpetrini at coredial.com>:
> Hello,
>> I've just started experimenting with nova backup and discovered that there
>> is a period of time during the snapshot where the instance becomes
>> unreachable. Is this behavior expected during a live snapshot? Is there
>> any
>> way to prevent this?
>> ___
>> John Petrini
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