About protecting against dedicated media server failures
Storage unit groups can be used to protect NetBackup against the failure of a single media server. Storage unit groups can also be used for load balancing across multiple media servers to ensure optimal backup and restore performance.
Table: Modes for configuring storage unit groups discusses the different modes in which you can configure the storage unit groups.
Table: Modes for configuring storage unit groups
Mode | Description |
|---|---|
Failover | In the failover mode, the first storage unit is always used, unless the media server is down. Excess jobs are queued rather than being directed to the next storage unit. The failover mode functions similarly to what would be seen if two media servers were configured as an active or a passive cluster. |
Prioritized | In the prioritized mode, the first available storage unit in the list is used. In this mode, jobs that exceed the total number the storage unit can handle, are directed to the next storage unit in the list. If the media server is down, all backups are directed to the next storage unit. |
Round robin | In the round robin mode, different storage units from the list are used in a cycle for each job. If each storage unit is on a different media server, this acts as a load balancing mechanism. |
Load balanced | The load balance mode only works with Flexible Disk and Media Manager storage unit types. In the load balance mode, NetBackup carries out checks on activity and resources available on each media. The check is carried out before the backup are directed to the media with the lightest load. |
As a best practice, when using prioritized and failover groups to configure two storage unit groups, use two media servers, as follows:
Configure each media server to have a single storage unit. For example, so Node A has STU A and Node B has STU B.
Configure two storage unit groups with the storage units in a specific order in each one. In this example, SUG AB contains STU A, followed by STU B. SUG AB contains STU B followed by STU A.
Backup policies are then evenly shared between SUG AB and SUG BA.
During operation, the backup traffic is normally shared between the two nodes, but if one node fails, all backups automatically go to the other node.