A backup for OpenStack images or instances includes the following stages:
- For each instance, create a Nova snapshot.
A Cinder snapshot is created for any volumes attached to the instance. Snapshots are crash consistent.
- Create volumes from Cinder volume snapshots.
- For an image backup, image reader is used to read the data directly and back it up to media.
A full backup is always performed for images, regardless of the backup type that is specified for the backup job.
- For volume backups, each volume is attached on the proxy, and then data is read and backed up to media. The following limits apply:
- For a VirtIO controller, up to 25 data volumes can be attached to the VSA proxy, occupying device slots vdb - vdz.
- For a SCSI controller, up to 4 data volumes can be attached to the VSA proxy, occupying device slots sdb - sdf. This limit is a libvirt version 1.2.17 limitation with RedHat 7.2.
These limits include any volumes already attached to the proxy. For example, if the VirtIO controller for a proxy already has vdb and vdc slots occupied, then only 23 data volumes can be attached.
- Back up the volumes, using CRC for incremental changes and directing data through the MediaAgent for the storage policy associated with the backup.
- Unmount, detach, and delete the volumes attached on the proxy created during the backup.
- Delete the snapshots created during the backup.
Last modified: 1/18/2019 3:52:41 PM