Friday, July 31, 2015

DAG Replication Woes

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I recently noticed that one of the hosts in my Exchange 2010 Database Availability Group was not properly replicating. Under each Mailbox, that host would show as failed. Based on what few errors were actually showing in the event log (The Microsoft Exchange Replication Service encountered a transient error while attempting to start a replication instance for Mailbox Database abcdefg\mail1. The copy will be set to failed. Error: The NetworkManager has not yet been initialized. Check the event logs to determine the cause.). Going to the logs just showed many logged instances of this exact message and not much else.

I went online and everything I read talked about disk space available on the failing host (in my case there is well over 1TB of free space) or network reachability issues (network monitoring has not shown any recent outage for either DAG host). So it looked to be another of those fun problems you won’t find an answer to until you know what exactly to search for, but you won’t know what to search for until after you resolve it.

What eventually fixed it (for the time being) was going into EMC, going to Organizational Configuration and then Mailbox and finally Mailbox Management. I highlighted each mailbox, then in the bottom pane selected the copy on the failed server and selected Suspend Database Copy, waited a few minutes, then selected Enable Database Copy. The Copy Status changed to Initializing for a few minutes, and then finally changed to Healthy.

I still haven’t gotten to the bottom of why this happened yet, and probably won’t in the foreseeable future as there just isn’t time to keep digging into something that is no longer broken, but I hope to have an answer eventually.


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