Exchange 2013 issue with maintenance mode

Occasional Contributor

Hey all.  Some basics first:

 

Two Exchange 2013 servers in a DAG (yes we are planning to upgrade soon!).  Both servers have all roles.  Two mailbox databases mdb01 and mdb02.  Latest CU.

 

We don't have any type of load balancing, basically all clients connect to the one in the Main Office, and if that goes offline, dns changes to point to the other at another location for backup and we manually make some changes for mail flow.

 

The issue!  I went to install the latest SU on the backup server.  Main Office Exchange had the two databases mounted in an active, healthy state, the backup had passive and healthy copies.  I put the backup server into maintenance mode and immediately clients on mdb02 couldn't update Outlook folders.  Outlook stated it was connected to Exchange but no folder was being updated.  mdb01 clients continued operating fine.

 

Main Office server still stated it had both mailbox databases mounted, active and in a healthy state.  Without installing the SU I took the backup server out of maintenance mode and clients on mdb02 starting working fine again.

 

So all clients were connecting to Main Officer server but those with mailboxes on mdb02 were not having Outlook update any folders.

 

I trawled the logs but could find nothing to indicate any problems.

 

I tested trying to migrate a mailbox from mdb2 to mdb1 and it failed; no other errors in the log:

25/10/2022 4:17:28 PM [mainoffice] Stage: FinalIncrementalSync. Percent complete: 95.
25/10/2022 4:17:28 PM [mainoffice] Copying per user read/unread data.
25/10/2022 4:17:28 PM [mainoffice] Per user read/unread data copied successfully.
25/10/2022 4:17:28 PM [mainoffice] Mailbox store finalization is complete.
25/10/2022 4:17:28 PM [mainoffice] SessionStatistics updated.
25/10/2022 4:17:28 PM [mainoffice] Verifying mailbox contents...
25/10/2022 4:17:29 PM [mainoffice] Mailbox contents verification complete: 38 folders, 22 items, 187.3 KB (191,748 bytes).
25/10/2022 4:17:29 PM [mainoffice] Waiting for mailbox changes to replicate.
25/10/2022 4:18:35 PM [mainoffice] Waiting for mailbox changes to replicate.
25/10/2022 4:19:35 PM [mainoffice] Waiting for mailbox changes to replicate.
25/10/2022 4:20:35 PM [mainoffice] Waiting for mailbox changes to replicate.
25/10/2022 4:21:35 PM [mainoffice] Waiting for mailbox changes to replicate.
25/10/2022 4:22:35 PM [mainoffice] Waiting for mailbox changes to replicate.
25/10/2022 4:23:35 PM [mainoffice] Waiting for mailbox changes to replicate.
25/10/2022 4:24:36 PM [mainoffice] Waiting for mailbox changes to replicate.
25/10/2022 4:25:36 PM [mainoffice] Waiting for mailbox changes to replicate.
25/10/2022 4:26:36 PM [mainoffice] Waiting for mailbox changes to replicate.
25/10/2022 4:27:36 PM [mainoffice] Fatal error MailboxDataReplicationFailedPermanentException has occurred.

 I fear database corruption of some sort!  Has anyone heard of this odd behaviour?

 

thanks

 

jc

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