Grant Fritchey (7/23/2013)
Backups from the secondary are somewhat redundant, and as you're discovering, not really possible. You can only run a FULL, proper, backup from the current primary. You can run log backups from any or all secondaries, but, understand that you'll need those logs, from all the secondaries, in order to do a point in time recovery. So, be very, very cautious about setting up secondary log backups. They will affect your primary server. I wrote a chapter in the book "Pro SQL Server 2012 Practices" on just doing backups and restores with Availability Groups.You can do a COPY_ONLY backup on the secondaries. But, you cannot use a COPY_ONLY backup as part of a point in time recovery. The entire concept behind the COPY_ONLY backup is to avoid dealing with the transaction log and differentials.
In a nutshell:
You have to enable backups on the secondary
set priority on the secondaries
schedule jobs on all secondaries
but make sure those jobs use T-SQL to do the backups and check for fn_hadr_backup_is_preferred_replica in order to determine if they are the correct backup server currently.
In short, it's pretty complicated.
Recommendation. Do all backups on the primary unless you identify a need for additional backups (high transaction volume or log backups causing blocking would be a good reason to split off the transaction log backups). Secondaries I wouldn't backup. They're just copies of the primary and should be synchronized (at some point if you're doing async).
THANK YOU GRANT! you just saved my buttocks! I have been looking for this type of answer for months. :w00t:
MCSE SQL Server 2012\2014\2016