Exchange '10 Multi-Site/SAN Design Across WAN

RTM2007 used Ask the Experts™
We currently are running Exchange 2010 that runs off SAN storage. Our primary configuration is in our main location that has 1 x CAS server, and 2 x DAG servers.

We are hosting Exchange for all our 2 offices abroad as well, meaning the users have to VPN here and open up Outlook or OWA from our main Exchange servers.

Might be looking to deploy individual Exchange servers for just those remote offices (they are currently in their own SGs) locally at their site however, would like to know how to best design this so that it is fast enough at their local site, but also can be backed up and accounted for from our main site.

Guess just throwing another CAS and DAG server at the remote site won't work unless it can specify which SGs/users?
Watch Question

Do more with

Expert Office
EXPERT OFFICE® is a registered trademark of EXPERTS EXCHANGE®

If bandwidth isn't an issue, your offices abroad should be connecting to their mailboxes at the main site via OA over the internet. I'm guessing that because they have to VPN that you don't have a direct IP route between the remote sites and the main site. But if you don't have that already, then how would you be running backups/DAG replication between these sites? I'm a bit confused about that.

However, if you have IP connectivity, and if you want to drop additional CAS/HT/MBX into the remote offices, it's doable. Put the DBs for RemoteA on the MBX role in RemoteA, same with RemoteB and their stuff on their server, and DAG them all back to the main office MBX servers. DAG the main office DBs to the remote office servers, too.

HT will sort itself out, really, just make sure you add the new HT servers to some new send connectors that look just like the one you already have.

For CAS, there's a powershell command you'll run against each of the new DBs you make, to set the RPCClientAccessServer to the appropriate value. But your OWA/OA/AS will still just be at the main office CAS.

Once you do this, and you have each DB on four servers in the DAG, you can stop doing backups. Set circular logging on the DBs and relax.


Bandwidth is an issue as some offices are limited in that country and Internet bandwidth is pretty expensive. In terms of routing would everything still have to hit the main production Exchange server (based on the MX record) and then get forwarded out to the appropriate DAG DB? Or would it simple make a "copy"?

If you're talking about one email domain, all the mail will come into the primary MX record. The HT role will pick it up from there, and deliver it to the correct MBX server/active database, possibly through other HT servers as necessary.

Then, the active DB ships the transaction logs back to every other server that holds a passive copy of that DB. Since bandwidth is an issue, this would be a double whammy.

Sounds like you want to keep all your Exchange in one location, and have those remote office users connect to their mailboxes over the internet, either with OWA, or with Outlook only if you have some serious transport and mailbox size caps in place.


Actually quite the opposite, would like to only keep Exchange servers where the according SGs/users are however, the concern is for backups, which are all done at one location.
In short, if you're going to back up remote servers to the main site, that backup traffic has to come across the network.

Does each location have its own distinct and separate email domain? If that's the case, then you can set up a separate Exchange organization in each location, and be fine with that.

Here's a thought: If you deploy three MBX role servers to each location, then you can set up a DAG for each location, and dispense with backups. That would eliminate the issue of expensive backup traffic across the network, and avoid the problem of having the even greater multi-site DAG replication traffic. You wouldn't have the DR capability that you'd have with a single DAG across locations, but you already don't have that, so you wouldn't be losing anything. You can do this whether each location uses a separate email domain or not.

Your bandwidth costs might be high enough that doing a DAG in each location makes financial sense over some time period, compared to the amount of money you'd spend on bandwidth for backups. You'll have to do the math on that yourself. Just be aware that each server in the DAG needs to have enough storage to handle all the databases it's running, active and passive.

Do more with

Expert Office
Submit tech questions to Ask the Experts™ at any time to receive solutions, advice, and new ideas from leading industry professionals.

Start 7-Day Free Trial