Veeam Backup & Replication • Veeam agent t-log backup causes availability group to go offline.

Hi,

case #07063030.

After upgrading to V12 we notice that our SQL Always-On Availability group becomes inaccessible during a transaction log backup job after running a database maintenance plan which optimize the indexes. This produces 100+ GB worth of transaction log backups. When the centrally managed Windows Agent job backs-up these transaction logs it consumes 99% of CPU on the secondary node of our cluster which brings the cluster down due to insufficient CPU resources for SQL server.

I've noticed that the priority of the veeamagent.exe process is set to normal. When manually setting it to 'Below normal', the cpu usage of veeamagent.exe drops to 60% which is enough to keep the cluster online.

When we run a full backup using the Windows agent, then the veeamagent.exe process is set to 'low' priority when it's running. I assume this is because I've configured the 'Throttle Agent backup activity' under the 'I/O Backup control' option on the protection group the SQL cluster is in.

The issue here seems to be that the transaction log backup job doesn't honour this throttling setting and always sets it to normal priority. In general this isn't an issue since transaction log backups are usually small, especially when set to 15 minutes as in our case. However, after running the maintenance job we have 100+ GB worth of transaction log backups and this causes the veeamagent.exe process to consume all CPU when setting to normal priority. I've no idea why though.

I've tried setting the process priority to ' below normal' or 'low' through the registry so it's persistent, but this is being ignored, Probably because it's set by the process itself.

Anyone else notice this behaviour?

Statistics: Posted by FrancWest — Jan 20, 2024 11:58 pm

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