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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?

Cheers,

Thomas Goirand (zigo)