Backup and Recovery Considerations With HSM

After a file has been migrated, when Backup backs up the client filesystem from this point forward, it only backs up the stub file that is left on the client machine. A Backup backup of a stub file does not recall the migrated file. When you recover a filesystem that contains a stub file for migrated data, Backup only recovers the stub file to the local disk. The migrated data is not recalled.

To recall a file to the client's local disk, open the file on the client machine. Backup automatically recalls the file from the migration store. If the media containing your migrated file is not currently mounted, Backup notifies the administrator.

Recovering an Accidentally Deleted Stub

If you accidentally delete a stub file on a migration client, you can restore the stub file from backup media within 60 days of the deletion. Recovering a stub file does not initiate a recall. If a stub file has not been recovered after 60 days, Backup removes the entry for the migrated file from the client index and no longer tracks the data.

Cloning Migration Media

To ensure that you can recover all your data, you should regularly clone your migration media. Because Backup only backs up the stub file on the client computer, not the migrated data itself, the clone might contain the only extra copy of a file. You can specify cloning to occur automatically after the migration process is completed by selecting the Migration Clone pool in the group resource you created for your migration clients. Clones of migration data must be written to volumes from a pool of type "migration clone." See "Using the Migration and Migration Clone Pools" for more information.

Performing a Super-Full Backup

To provide additional backup protection for migrated files, you should regularly perform super-full backups of your migration clients. A super-full backup clones both the most recent full backup of a save set and all the migration save sets, so it contains the stub file on the client and the data in the migration store. To perform a super-full backup, become root on the Backup server, then enter the following command from the shell prompt:

# nsrclone -c client-name -N save-set-name