The Road to Exchange 2010: Active Directory and Exchange Part 3
In part 1 we’ve discussed the Exchange Mode, Domain Controllers and Schema Master compatibility. In part 2 we’ve discussed the Global Catalog and the Domain and Forest Functional level up to Windows 2008. So, that leaves us with Windows Server 2008 R2.
During the time it took to write this series of blogs a lot more information was made available. Especially the Exchange Server Supportability Matrix was a huge help. Actually, the previous lack of such a page with all this information in one place was one of the reasons to do this series.
Windows Server 2008 R2
Obviously the Exchange mode is something that is only relevant with Exchange 2000/2003 and nothing with this release of Windows.
The compatibility with domain controllers though, is another story. Only Exchange 2007 Service Pack 1 with Rollup update 9 for SP1 (and higher) will work correctly with Windows 2008 R2 domain controllers. You could exclude the specific Domain Controller, when you have other DC’s in your domain/site with the Exchange Server. But I would not recommend it as this can impact the availability of any DC for Exchange and directly the availability of Exchange, next to the extra administrative effort you will have to take. I would only do this (and have done this) during transitional phases.
The same requirement is valid for the Schema Master and Global Catalog, so only Exchange 2007 SP1 with rollup 9 and higher. You also can exclude the specific Global Catalogs, but it comes with the same warning label as with Domain Controllers mentioned above. The Schema Master is a Forest FSMO role, so you can have only one in your AD forest and Exchange organization. No cheating possible here. 😉
The Domain and Forest Functional Level of Windows Server 2008 R2 feels a bit weird to me, we didn’t have this with Windows 2003 R2. So, there’s probably something really happening here. For a overview of the new possibilities of DFL/FFL 2008 R2, look at this page.
Both the DFL/FFL of Windows 2008 R2 are only supported by Exchange 2007 SP1 with Rollup update 9 and higher. Exchange 2000 already couldn’t work with a domain with exclusive Windows 2008 (R2) server, so this is a logical progression. Exchange 2003 could work with Windows 2008 DC’s, but not with 2008 R2 DC’s, and this logically excludes both 2008 R2 DFL/FFL.
When we revisit our compatibility matrices and add Windows 2008 R2 to it, we get:
Conclusion
Exchange and Active Directory on their own can be complex to maintain. But combining the specific requirements and (im)possibilities, it can be a maze. Especially for those who have to maintain and transition their multi domain forest to newer versions of Exchange and Windows and you have a variety of different versions of Windows and Domain Functional Levels.
But there is one relatively safe route: Windows Server 2003 with at least SP2. This is the golden version of Windows for Exchange 2000 to 2010. The Domain Controller Global Catalog function and the FSMO role of Schema Master can al reside on this version and all versions of Exchange can function with it. For the Domain Functional Level 2003 is the safest level, when considering Exchange transition from 2000 to eventually 2010. The 2003 Forest Functional level also works with al version of Exchange.
For transition paths regarding only Exchange co-existence check this post.
I hope that you find these blog posts helpful in transitioning your Exchange organization to any versions available within any Active directory environment. If you have questions or comments on these posts (or just to say hi), feel free to contact me!
Disclaimer: the information here and in previous posts on this subject is presented as-is and could be subject to change. The information on Exchange 2010 is in some cases still in writing and could contain facts that have changed or will change. Recheck those facts before implementing Exchange 2010 when it has reached general availability, which will be announced at TechEd 2009 in Berlin and other events.
Further Reading
Exchange Server Supportability Matrix
What's New in Active Directory Domain Services
The Road to Exchange 2010: Active Directory and Exchange Part 1
The Road to Exchange 2010: Active Directory and Exchange Part 2