Add And Remove a Server from DAG?

[maybeimaleo]

I'm going to lay it all out for everyone:

Me and my staff have limited experience with Exchange of any flavor. While we are in the middle of a SAN migration we have discovered that one of our servers in the DAG.... actually, we have two servers, one holds all of the DBs (let's call it the primary)and the other holds the replica.

Both servers are VMs (5.1, fully patched). The replica was created with Raw Device Mappings for some stupid reason. We need to remove them so that we can remove the links to the old storage. We could V2V the server but it would have to be offline. Considering the server has 2TB of disk space the conversion would take too long. Our consulting partners suggest that we build a new server as a replica and the shutdown the current one.

My question is,how do I build the server?
How do I safely remove the current one?
If I were to shut down the replica and V2V it, would the primary server freak out?
Would Exchange stop running?

Uh, Help?

 

[ShackDaddy]

My advice would be to get someone to help out with the DAG bit who knows their way around it. That being said:

The simplest path forward, given your expertise, is to simply do the V2V.

If you took the DAG node with the passive database offline for a day or two, logs would accumulate on the active server and would be sent to the passive server when it came online and applied to the replica. It could take a day or two to catch up, but probably less. Worst case scenario: you'd have to reseed the replica, but that's better than having your mail system offline.

Normally when you have a two-node DAG, a third server, typically a DC, plays a "quorum" role and as long as the active node and the quorum are online, taking the passive node offline for a couple of days for a V-to-V shouldn't bring the database copies on the primary/active server offline.

Dave Shackelford
ThirdTier.net

 

[maybeimaleo]

Ugh... the V2V doesn't sound very comforting as I am not sure if the logs would fill up the exchange database or not. WOuld we have to stop the backups as well?

 

[ShackDaddy]

The log generation simply corresponds to the number of changes to the database. Unless you are down to the last 5% of your storage on the logging volume, having the passive server offline for 2-5 days would not cause you to run out of space. If it looked like there was a risk, you'd another backup, then simply remove the passive DAG node from the DAG, dismount the databases, delete the logs while they were dismounted, and remount them, taking an immediate backup afterward.

You would not need to stop the backups, because when you have DAGs, backups only cause logs to truncate after the passive DAG member signals that those logs have already been committed.

Dave Shackelford
ThirdTier.net

 

[maybeimaleo]

Sweet. We are going to go with the V2V.

 

[maybeimaleo]

Everything worked like a champ!

 

[ShackDaddy]

Glad to hear it!

Dave Shackelford
ThirdTier.net