Reinstalling Exchange 2010 (w/ DAG) After A Server Failure

Well, I learned this the one the hard way. :)

I had (operative word…’had’) an a couple of Exchange 2010 VM’s running in my lab – DAG configured and all…until I was re-balancing storage, adding/removing LUN’s, etc… and accidentally deleted the LUN that had the VHD for the 2nd server in my Exchange 2010 DAG on it (as well as a few other things…*sigh*)

Fun times.

I debated just blowing the whole thing away and starting over – opening ADSI Edit and just killing it there…but alas, I thought I’d figure this one out and maybe learn something in the process.  Well, I did – and I’ll share it here for you (and for me should I ever do it again).

I got it working again, after running into a few other issues (this process gets slightly more complicated when a DAG is configured, as you might expect).

First things first…

You’ll have to setup your 2nd server again – use the same OS, same SP level, etc…  If you originally had it running on Server 2008…don’t try to get re-running on Server 2008 R2.  Name the server the same, same IP configuration and of course add it to the domain.

Good general guide here:

The next thing I did was just run setup /m:RecoverServer on my new Exchange box.  I knew I was going to be missing some pre-req’s and i was.  You need .NET 3.5 and in my case an Outlook 2007 Filter Driver.  Once I got those installed, I re-ran the setup from the 2nd server again.

Then I ran into the DAG issue…

When you run the setup (which will process entirely through the command line), you’ll get an error on the prerequisite check for the mailbox role.  It will detect that a DAG was configured and the setup will terminate.

So, what do you do now?

Go back over to the first Exchange Server and open the Exchange Shell.



Run this command for ALL servers that were in the DAG (in your case substitute your server names where I have EXCH-02).

Now, you’ll need to clean up the cluster:


Next, go into the Exchange Management Console and manually remove the DAG’s from the GUI – simple right click and ‘remove’ should suffice.

Then, back on your new server – re-run the setup /m:RecoverServer command and you should be golden now.  It will run it’s course and eventually complete requiring a reboot:


Back in business!


Good Luck!