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Can Hub Transport Co-Exist on a Domain Controller?

We are co-locating our Exchange Servers and need to have high availability.  The current configuration is two clustered  Exchange 2007 servers with a separate hub transport/CAS server. The contemplated configuration is two Exchange 2010 servers and two domain controllers configured to DAG.  To achieve load balancing can I put the Hub Transport role on the domain controllers?  I know best practice is to not to mix the two but this is a small operation, only 100 users.  Just trying to avoid buying yet more hardware (a load balancer).
1 Solution
Yes, you can put any Exchange role on a domain controller. Microsoft does not recommend this mainly due to issues of load as both active directory and Exchange generate load. However, if you properly size your hardware you will be fine.

As a side note, small business server 2003, 2008, and 2011 have all had Exchange (as well as SharePoint) in a one box installation with a domain controller for years.


I think a better config would be the two Exchange 2010 servers running all 3 roles with either a hardware load balancer or CAS Array (basically DNS Round robin)

Exchange and AD will run on the same sever, but there are a lot of performance problems.  
Delphineous SilverwingGood Ol' GeekCommented:
The official word from Microsoft is this "is not a recommended configuration".  When you run the Exchange Analyzer Tool, it is going to tell you that.

As already mentioned, Small Business Server (SBS) is an all-in-one configuration with the Domain Controller, Exchange, SQL, and other services wrapped into one server.  But this SBS server is specially configured to integrate those services; an integration that does not occur when the services are installed separately on a regular Windows server.

Long story short, sure you can put a HUB role on a Domain Controller.  I do not suggest putting Client Access or Mailbox roles on the Domain Controller though.
Herb-AvoreAuthor Commented:
While the other offered solutions are no doubt based on good experience I am going with this posting.  For a couple of years now I have been running a clustered Exchange 2007 arrangement along with a Hub Transport / CAS box that was an Optiplex 755 workstation.  We've had no load balancing issues so I'm hopeful that our small shop can accommodate to this hybrid arrangement.

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