While applying the patch to SQL instance, I cluster, sometimes we get warning “Cluster Resource DLL Update Restart Check.” If we check Detail.txt file in setup logs, we will find below.
(10) 2018-01-20 16:51:10 Slp: Rule ‘Cluster_IsLocalNodeGroupOwner’ detection result: NodeOwnsClusterGroup=True
(10) 2018-01-20 16:51:10 Slp: Evaluating rule : Cluster_IsLocalNodeGroupOwner
(10) 2018-01-20 16:51:10 Slp: Rule running on machine: SQLVMNODE2
(10) 2018-01-20 16:51:10 Slp: Rule evaluation done : Warning
(10) 2018-01-20 16:51:10 Slp: Rule evaluation message: The local computer is an owner of a cluster group that contains the SQL Server service, Analysis Services service or a generic service for a failover cluster instance. If you continue, the SQL Server instances may be taken offline causing downtime while the patch is being applied.
In the wizard its just a warning and allows us to move next. But if we read the warning then its very evident that it is going to impact other instances which are running on this node.
One of my clients had downtime for 10 other instances which were of the previous version of SQL and earlier patches didn’t cause any issue. So, they were confident that there would be no impact on other SQL instances.
As we can see that the upgrade rules will warn us that any other SQL instances active on this node might be restarted due to cluster resource DLL update. This is especially important if you have not planned on those other instances being restarted. So, you should note it and factor it into your upgrade plans.
Reference: Pinal Dave (https://blog.sqlauthority.com)