Would it be supported in an Exchange 2007 environment to run some roles on Windows Server 2003 x64, and some roles on Windows Server 2008 R2? Specifically, would it be supported by Microsoft to keep our mailbox servers on Windows Server 2003, but migrate our CAS/HT server to Windows Server 2008 R2? Thank you, -Craig

Yes that is a supported configuration. If you were to attempt to install a cluster on two different OS's that would be an unsupported configuration however (OS wouldn't even allow you to-do it). Hope this helps. -Chris*** Chris Raschke MCITP:EA | MCITP:EMA | MCSE | MCTS | Security+

Hi Craig, Above gave good information, any other issue? Regards! Gavin TechNet Subscriber Support in forum If you have any feedback on our support, please contact tngfb@microsoft.com Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

This is supported and Windows 2008 R2 can give you benefits over Windows Server 2003. CAS user concurrency on Windows 2008 is far greater for example. The one thing I would say if you have a large Enterprise and have load balancing and clustering in place. Is keep it streamlined. So don't have a load balanced array of 2003/2008 CAS servers for example (although you can...) Keep whatever OS design decisions you make exclusive to each Exchange Server role. OliverOliver Moazzezi | Exchange MVP, MCSA:M, MCITP:Exchange 2010, BA (Hons) Anim | http://www.exchange2010.com | http://www.cobweb.com | http://twitter.com/OliverMoazzezi

With CCR specifically, both have both have to be the same.

With CCR specifically, both have both have to be the same.