If your Exchange 2010 deployment utilizes a DAG in two or more Active Directory sites you may have run into situation where the Primary Active Manager (PAM) is unexpectedly located on a DAG node that resides in another site. The PAM, aka the “cluster group” will shift around as necessary among the members of your DAG for various reasons. So you ask, “Who moved my PAM?”:
- You may have moved it as part of DAG maintenance.
- There was problem with the DAG node hosting the PAM, such as errors in the ESE or a storage problem, and the role moved to a server in an alternate site.
- A network communications error occurred, affecting the cluster service heartbeat, causing the PAM to move to what it believes is a surviving member of the DAG.
Unfortunately there is no way to add a server preference to the PAM role. It would be nice to be able to tell the PAM to try and stay on a server at a preferred active directory site. The only thing that you can do is to block a DAG member from having database copies activated on it with the following command:
Set-MailboxServer –Identity EX02 -DatabaseCopyAutoActivationPolicy Blocked
This isn’t much help as it defeats the purpose of redundancy in the DAG. As long as you are running your multi-site DAG with DAC mode enable, you shouldn’t have a problem with a split brain scenario. However the PAM does coordinate database activation and is the quorum resource so getting it back to you preferred site is probably something you should strive towards. It is safe to manually move this role to another DAG member during production hours. Use the following commands:
Move-ClusterGroup -Name <Group Name> -Node <Node Name> -Cluster <Cluster Name>
Keep an eye on that PAM!