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

Availability Group DMVs

Adrian Buckman shows off a few Availability Group DMVs: Whilst I was combing through various combinations of sys.dm_hadr and sys.Availability I stumbled across a couple of gems that I thought would be nice to share. sys.dm_hadr_cluster sys.dm_hadr_cluster_members sys.dm_hadr_cluster_networks Read on for usage examples.

Read More

Performance Problems Due To Readable Secondaries

Paul Randal describes a problem when you create a readable secondary on an Availability Group: Yesterday I blogged about log shipping performance issues and mentioned a performance problem that can be caused by using availability group readable secondaries, and then realized I hadn’t blogged about the problem, only described it in our Insider newsletter. So here’s […]

Read More

Categories