Around a couple of years back we did an Exchange 2010 HA project for a client in Florida, it was a simple 2 Mailbox server and 2 CAS/HT server highly available Exchange 2010 setup. So this client called us a few days back stating that some of his exchange databases are dismounted and mail flow was interrupted. I checked the server to find some interesting issues which I wanted to document here.
I started with Exchange Management console and found that the databases which were part of DAG were running successfully on the other server but couple of databases which were local to one of the server were dismounted, as first try, I simply tried to mount them and they failed to mount with the following error
Microsoft Exchange Error
Failed to mount database ‘Mailbox Database DB1’.
Mailbox Database DB1
Database ‘Mailbox Database DB1’ can’t be mounted on server ‘EX-MB1.domain.org’ due to a previous error: Failed to determine the mount status of the active database copy. Verify that the underlying cause of the error has been corrected before attempting to mount the database. The error can be ignored and the mount allowed if Mount-Database is reissued with the -Force switch.
So as we can see in last line of error that we do have an option to use Mount-Database -Force switch to force mount the database but I usually do not recommend force mounting a database as Exchange must have unmounted it to prevent some damage. So I wanted to fix the issue, it was clearly a DAG issue. I went ahead and checked the services on the problem server and found that I was unable to start the cluster service.
As a next step, I decided to remove the problem server out of the database availability group, from Exchange Management Console (EMC) and I got the following error
There was a problem changing the quorum model for database availability group FirstDAG. Error: An Active Manager operation failed. Error An error occurred while attempting a cluster operation. Error: Cluster API ‘”SetClusterQuorumResource() failed with 0x1725. Error: A quorum of cluster nodes was not present to form a cluster”‘ failed..
The operation wasn’t successful because an error was encountered. You may find more details in log file “C:\ExchangeSetupLogs\DagTasks\dagtask_2016-12-07_10-06-15.647_remove-databaseavailabiltygroupserver.log”.
Exchange Management Shell command attempted:
Remove-DatabaseAvailabilityGroupServer -MailboxServer ‘EX-MB1’ -Identity ‘FirstDAG’
Elapsed Time: 00:00:00
So to take care of this error, I used the same command from PowerShell by adding a switch -configurationonly (Refer below)
Remove-DatabaseAvailabilityGroupServer -Identity DAG -MailboxServer EX2 -ConfigurationOnly
After this, I tried to start the Cluster service but it still failed, This time I decided to actually evict the server directly from Failover cluster manager. Refer the screen shot below
After taking the node off the cluster, I was able to successfully start the Cluster Service on problem server. As the service got started I was able to mount all the databases on the respective servers without any error message. As the next step we had to add the problem server back to DAG which we were able to do easily from EMC.
Once my problem server was added back to the DAG, I started adding my database copies to the problem server (which was most likely fixed now). But as I started that I ran into few more errors. Please refer to following article which talks about the errors I faced while adding the database copies.
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