Add a new config option "backup_ceph_max_snapshots" to only keep
the last n snapshots of a volume backup on the source volume storage
to save disk space.
By default, the current behavior of keeping all snapshots is used, but
can now be adjusted as requested.
Commit bc9ab142da919087c71525978f960115ff0259b9 changed the previous
behavior of keeping only the last snapshot to keeping all snapshots of
a backup. However, this can take up much more disk space on the
source volume storage.
If enabled, the driver checks the number of snapshots of a volume backup
after successful creation of a new snapshot and removes older ones, so
that only the n most recent snapshots are kept on the source storage.
This change also creates a new special case which was not present
before: If a user deletes at least n backup snapshots, the next
incremental snapshot creation would fail (due to how RBD works).
This will be handled by forcing a full backup instead.
Therefore, this commit introduces a configurable tradeoff between
required space on the source volume storage and a potentially longer
backup time.
Change-Id: Ief71e6e62ccc0654f4e1e71ccc53df66d5ffbfac
Related-Bug: #1703011
Signed-off-by: Jan Hartkopf <jhartkopf@inovex.de>
03cbcd3cd0