Availability Group Backup Preferences

Shaun Stuart points out that the Backup Preferences tab of the Availability Group Properties for an AG is a little tricky:

The default, and the way my AG was configured, was Prefer Secondary. As the image shows, this means backups will be made on the secondary, unless the secondary is unavailable, in which case, they will be made on the primary.

There are a couple of things to note when you use this setting:

  1. Full backups made on the secondary are Copy Only backups. This means they won’t reset the differential bitmap and your differentials will continue to increase in size until a full backup is made on the primary.

  2. Differential backups cannot be made on the secondary.

  3. Transaction log backups can be made on the secondary and they do clear the log, so your log file will not continue to grow.

Read on for more details.

Related Posts

Removing A Database From An AG

Erin Stellato walks us through the process of removing a database from an Availability Group and then re-adding it later: I recently had a scenario in a two-node Availability Group where multiple large-batch modification queries were executed and created a large redo queue on the replica.  The storage on the replica is slower than that […]

Read More

Missing Backup Directory When Trying To Upgrade SQL Server

Lori Brown walks us through the solution to an error she experienced: I was recently performing an in-place upgrade of SQL 2008 R2 to SQL 2014 on one of my client’s servers.  I have done a ton of successful and uneventful in-place upgrades and was surprised when the upgrade failed with the error message:  “Failed to […]

Read More

Categories