How Backup Selects a Storage Volume for Relabeling

Backup data is destined for volumes from a specific pool. When the data is ready to be written, Backup monitors the active devices to locate a volume from the appropriate pool.

If only one volume from the pool is mounted and appendable, the data is directed to that volume.

If two volumes from the same pool are mounted on devices, Backup considers the following factors to guide its volume selection:

• The expiration date of the volume

  By default, the volume expiration date is set at two years after the date on which the storage volume was labeled (or relabeled). To override this default setting, change the volume's expiration date in the Devices resource. If the default setting is overridden, Backup checks to ensure that the volume expiration date is farther in the future than the date on which the save set is set to exceed its retention policy. If Backup finds that the volume expiration date is later than the retention policy, then the save set is written to the volume. Otherwise, Backup does not write the save set to the volume. (This checking behavior does not occur if the expiration date of the volume is not overridden.)

• The volume mode

  • If a mounted, appendable volume from the appropriate pool is available, Backup writes to it.

  • If there is no appendable volume of the appropriate pool available (and if you enabled auto media management), Backup recycles and then writes to a mounted, recyclable volume from the appropriate pool as a second choice. (Backup does not consider writing to a mounted, recyclable volume that belongs to a different pool.)

  • If no volumes of the pool are available (and if you did not enable auto media management), Backup labels, mounts, and writes to a new, unlabeled volume or a volume that does not have a Backup label.

• The volume label time, which is the time when the volume was labeled

  Volumes with the oldest label time are selected before volumes that were labeled more recently.

• The number of sessions currently writing to the device

If Backup cannot find a mounted volume from the appropriate pool, a mount request is initiated. If auto media management is not enabled or if Backup has only standalone devices available, mount requests continue to be generated until a volume is mounted and backup can begin.