Always on Availability Groups

Bacula Enterprise Only

This solution is only available for Bacula Enterprise. For subscription inquiries, please reach out to sales@baculasystems.com.

Availability groups can be created in MSSQL to provide high data availability over WSFC cluster nodes, as detailed in this article: https://docs.microsoft.com/en-us/sql/database-engine/availability-groups/windows/overview-of-always-on-availability-groups-sql-server?view=sql-server-2017

It can be interesting depending on the system scale to perform backups on secondary replicas to free up time and resource costs from the primary replica. The Bacula MSSQL Plugin is compatible with this type of architecture, with some restrictions.

Backup Preferences and Replica Selection

When availability group(s) are defined, automated backup preference should also be specified to indicate the type of backup strategy (prefer secondary, primary only, etc.). The MSSQL plugin enforces this preference, only allowing backup of the preferred replica.

Note that depending on replica, not all backup type are allowed. Secondary will support copy-only full database backups and log backups while differential is not supported. This needs to be taken in account when creating Bacula’s backup Jobs. Refer to this article for more details: https://docs.microsoft.com/en-us/sql/database-engine/availability-groups/windows/active-secondaries-backup-on-secondary-replicas-always-on-availability-groups?view=sql-server-2017

Restore Restrictions and Workflow

Database restores can not be performed when they are part of one or many availability groups. This is detected by the plugin and the database restore will be skipped when this is the case. To workaround this, you need to remove the database from the availability group(s), then restore the database and eventually put it back in its original availability group(s). More details can be found here: https://social.technet.microsoft.com/wiki/contents/articles/28148.restoring-a-backup-database-to-an-availability-group-sql-server.aspx