I faced a very strange case with Exchange DAG, I was doing a site resiliency test I failed over to the DR site successfully and then I failed back to the main site, after failing back I found that the DAG was in a state that looks like split brain syndrome although the DAG was running in DAC mode.
the symptoms were as follows:
From the DR mailbox server:
- Cluster Console only showed this node while the active nodes were not present.
- From EMC the copies on the DR server were healthy.
From the Main site mailbox servers:
- Cluster console showed the three nodes but the DR node was stopped, and the option to start it was grayed out.
- From EMC the copies on the DR server were failed.
The fix was as follows:
run the following command: Cluster
That's It !