The server default policy enables client nodes to back up data to disk storage pools on the server. As an alternative, you may configure a policy to store client data directly in tape storage pools in order to reduce contention for disk resources. If you back up directly to tape, the number of clients that can back up data at the same time is equal to the number of drives available to the storage pool (through the mount limit of the device class). For example, if you have one drive, only one client at a time can back up data.
The direct-to-tape backup eliminates the need to migrate data from disk to tape. On the other hand, performance of tape drives is often lower when backing up directly to tape than when backing up to disk and then migrating to tape. Backing up data directly to tape usually means more starting and stopping of the tape drive. Backing up to disk then migrating to tape usually means the tape drive moves more continuously, meaning better performance.
At the server command line, you may define a new policy domain that enables client nodes to back up or archive data directly to tape storage pools. For example, you may define a policy domain named DIR2TAPE with the following steps:
copy domain standard dir2tape
This command creates the DIR2TAPE policy domain that contains a default policy set, management class, backup and archive copy group, each named STANDARD.
update copygroup dir2tape standard standard destination=tapepool
To use a tape storage pool named TAPEPOOL for archive, enter the following command:
update copygroup dir2tape standard standard type=archive destination=tapepool
activate policyset dir2tape standard
update node tapeuser1 domain=dir2tape