03cbcd3cd0
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>
3.0 KiB
Ceph backup driver
The Ceph backup driver backs up volumes of any type to a Ceph back-end store. The driver can also detect whether the volume to be backed up is a Ceph RBD volume, and if so, it tries to perform incremental and differential backups.
For source Ceph RBD volumes, you can perform backups within the same Ceph pool (not recommended). You can also perform backups between different Ceph pools and between different Ceph clusters.
At the time of writing, differential backup support in Ceph/librbd was quite new. This driver attempts a differential backup in the first instance. If the differential backup fails, the driver falls back to full backup/copy.
If incremental backups are used, multiple backups of the same volume are stored as snapshots so that minimal space is consumed in the backup store. It takes far less time to restore a volume than to take a full copy.
By default, all incremental backups are held on the source volume
storage, which can take up much disk space on the usually more expensive
primary storage compared to backup storage. Enabling the option
backup_ceph_max_snapshots can save disk space on the source
volume storage by only keeping a limited number of snapshots per backup
volume. After every successful creation of a new incremental backup, the
Ceph backup driver will then ensure that excess snapshots of the
corresponding backup volume are deleted so that only the
backup_ceph_max_snapshots most recent snapshots are kept on
the primary storage. However, this can cause incremental backups to
automatically become full backups instead if a user manually deleted at
least backup_ceph_max_snapshots incremental backups. In
that case the next snapshot, being a full backup, will require more disk
space on the backup storage and will take longer to complete than an
incremental backup would have.
Thus, the option allows to configure a tradeoff between required space on the source volume storage and required space on the backup storage as well as a longer backup process under the above conditions.
Note
Block Storage enables you to:
- Restore to a new volume, which is the default and recommended action.
- Restore to the original volume from which the backup was taken. The restore action takes a full copy because this is the safest action.
To enable the Ceph backup driver, include the following option in the
cinder.conf file:
backup_driver = cinder.backup.drivers.ceph.CephBackupDriverThe following configuration options are available for the Ceph backup driver.
cinder.backup.drivers.ceph
This example shows the default options for the Ceph backup driver.
backup_ceph_conf=/etc/ceph/ceph.conf
backup_ceph_user = cinder-backup
backup_ceph_chunk_size = 134217728
backup_ceph_pool = backups
backup_ceph_stripe_unit = 0
backup_ceph_stripe_count = 0
backup_ceph_max_snapshots = 0