Open Stack

On Thu, Jun 14, 2018 at 11:13:22AM +0200, Thomas Goirand wrote:
> Hi,
> 
> When using cinder-backup, it first makes a snapshot, then sends the
> backup wherever it's configured. The issue is, to perform a backup, one
> needs to make a snapshot of a volume, meaning that one needs the size of
> the volume as empty space to be able to make the snapshot.
> 
> So, let's say I have a cinder volume of 1 TB, this mean I need 1 TB as
> empty space on the volume node so I can do a backup of that volume.
> 
> My question is: is there a way to tell cinder to reserve an amount of
> space for this kind of operation? The only thing I saw was
> reserved_percentage, but this looks like for thin provisioning only. If
> this doesn't exist, would such new option be accepted by the Cinder
> community, as a per volume node option? Or should we do it as a global
> setting?
> 

I don't believe we have this as a setting anywhere today.

It would be best as a per-backend (or backend_defaults) setting as some
backends can create volumes from snapshots without consuming any extra space,
while others like you point out with LVM needing to allocate a considerable
amount of space.

Maybe someone else can chime in if they are aware of another way this is
already being handled, but I have not had to deal with it, so I'm not aware of
anything.