You can protect SQL Server databases in AlwaysOn Availability Groups using the Windows Agent and SQL Server Plug-in, or the Windows Agent and Image Plug-in version 7.5 or later.
If you back up a database in a secondary replica, a copy-only backup of the database is performed. Copy-only backups do not affect the sequence of conventional SQL Server backups. Microsoft only supports copy-only backups of secondary databases (see http://msdn.microsoft.com/en-us/library/hh245119.aspx).
Note: If a backup job includes secondary databases and databases that are not in a secondary replica, a copy-only backup will be performed for all databases in the job. Do not include a secondary database in the same job as a standalone database.
To protect SQL Server databases in AlwaysOn Availability Groups, do one of the following:
•Install the Windows Agent and plug-in on the server where the primary replica is hosted.
If you use the SQL Server Plug-in, you can run a full backup of the primary databases, followed by full or transaction log backups. If the primary replica becomes a secondary replica after a failover, the Agent automatically runs copy-only database backups instead of full backups. Transaction log backups remain the same.
If you use Image Plug-in version 7.5 or later, you can run application-consistent image backups of the volumes with database files. If the primary replica becomes a secondary replica after a failover, the Agent automatically runs copy-only backups.
•Install the Windows Agent and plug-in on a server where a secondary replica is hosted. This backup strategy offloads backup processing to a non-primary server.
If you use the SQL Server Plug-in, you can run a copy-only backup of the secondary database, followed by copy-only or transaction log backups. If the secondary replica becomes the primary replica after a failover, the Agent automatically runs full backups instead of copy-only backups. Transaction log backups remain the same.
If you use Image Plug-in version 7.5 or later, you can run application-consistent image backups of the volumes with secondary database files. The Agent automatically runs copy-only backups of secondary database files. If the secondary replica becomes the primary replica after a failover, the Agent automatically runs full backups instead of copy-only backups.
Note: If the availability mode of the secondary replica is asynchronous-commit, transaction logs on the secondary database could lag behind the primary replica database. If the secondary database is being backed up, data loss could occur.
•Install the Windows Agent and plug-in on the primary replica server and on secondary replica servers. This strategy ensures that backups continue even if one of the replicas is down.
If you use the SQL Server Plug-in, you can run a full backup on the primary replica, followed by full or transaction log backups. You can also run copy-only backups on the secondary replicas, followed by copy-only or transaction log backups.
If you use Image Plug-in version 7.5 or later, you can run application-consistent image backups on both the primary replica server and the secondary replica server. The Agent automatically runs copy-only backups of secondary databases.
If a SQL database in an AlwaysOn Availability Group is hosted on a SQL Server Failover Cluster Instance, install the Agent, SQL Server Plug-in and Cluster Plug-in on each physical node, and configure jobs on the virtual node. Full backups will run if the database is a primary database, and copy-only backups will run if the database is a secondary database.
Note: Only GPT disks are supported for Image backups (including application-consistent Image backups of volumes with database files) in a cluster.
For information about restoring SQL Server databases in AlwaysOn Availability Groups, see Restore databases in AlwaysOn Availability Groups.