Exchange 2010 - DAGs and other questions

Posted on 2011-03-10
Last Modified: 2012-05-11
I'm running in a test env now. I've successfully been able to migrate an exchange 2003 server over to exchange 2010.

My Exchange 2003 solution (in lab and in production) is running on a single server. I have several hundred users but the vast majority of them infrequently check their mail and when they do, we have them set up as POP users (too complicated to explain why). We have had no performance issues with this current Ex2003 setup.
In the new Ex2010 solution, there will be just a few (maybe 50-100 users) who will need to connect to the server via MAPI (Outlook Anywhere), and maybe 50 of these users have smart phones that will need to connect to Exchange as well. The rest will all be POP or connecting via OWA.

I have a list of questions that might very well overlap, but I'm trying to get some big picture vision here.

 I'm thinking that what I will do is have two physical servers. One will run all Exchange Roles as well as be the primary DC.  The second server will be my backup DC as well as my backup Exchange server to hook up to for DAGs. Is this a reasonable solution?

If I understand DAG's correctly, I need to have Exchange running on a second server in order for the DAG's  to work correctly, yes?

Am I correct in assuming that a POP user connecting to an Exchange server will use less server resources then say a full-fledged Outlook MAPI connection?

The reason I want to keep the number of physical servers down is because we are renting these servers from Rackspace, we don't run these servers in house. So each additional server is a pretty big expense for us.
I want to create this solution with the fewest number of servers possible.  I know two servers might not be optimal - but I need to know if this will work, and how far from optimal it is.  

Thanks for your suggestions and thoughts.

Question by:nachtmsk
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Accepted Solution

sjepson earned 500 total points
ID: 35096409
Yes you do require two servers running Exchange 2010 to support a basic DAG setup.

However, if you host all roles including CAS on the same server as the mailbox then you cannot use Microsoft load balancing to create a redundant CAS setup as well. This is because Exchange servers setup as DAGs use a subset of clustering which is not compatible with Network load balancing.



Expert Comment

ID: 35096477
Not sure of the resource requirements of POP3. Both POP3 and MAPI (if Outlook is set to cached mode) will pull all data from the Exchagne server and then store in a local message cache. So there shouldn't be too much difference between POP3 and Outlook in this scenario. If Outlook is not cached mode then it will generate more server I/O.


Author Comment

ID: 35096517
Steve --

what is "a redundant CAS" setup exactly? You mean like automated failover?  So I'd have to manually select the 'backed up' DB in the DAG in the event of a DB problem?

Expert Comment

ID: 35096877
Good question.

When an Outlook client starts it asks Active Directory what the CAS server or array end point addresses is for the site. Normally with separate CAS hardware you would form an NLB array and then failover and load balancing is taken care of. When you cannot configure NLB because your hardware is part of a mailbox DAG and you don't want an external NLB device then at the very least a reboot of the Outlook client will be required to connect to the new CAS IP address. Not sure if any further intervention is necessary for Exchange to tell AD what the new CAS end point is, if it refreshes automagically or if it does DNS round robin.


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