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My production system has two Windows Server 2003 R2 servers acting as domain controllers. Can I add a Windows Server 2008 DC to the existing domain without changing the schema? This is a similar question to but in that case, the 2008 server being added was not a domain controller.

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up vote 6 down vote accepted

No. The process for adding a 2008 DC requires schema updates. Member servers are not a problem, but a Domain Controller is another thing entirely.

That said, generally speaking schema updates like those that come with Server 2008 are harmless to lower versions. Do you have a specific problem with the schema updates that come with 2008?

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I'm fairly confident that schema updates are always backwards-compatible. The only problem would stem from an application that checks for the domain level as an 'equals' ("=") rather than a 'greater-than-or-equal' ("<=") (as in 'domain level is 2003 native' rather than 'at least 2003'). – gWaldo Sep 10 '10 at 19:40
@gwaldo It's schema version, not Functional Level. The Schema gets updated the moment the right 'adprep' call is made, so you can have a 2008-level schema but still 2003 functional level. If @Knox is concerned about schema issues, functional level doesn't matter. – sysadmin1138 Sep 10 '10 at 19:44
You're quite right. – gWaldo Sep 10 '10 at 20:28
well, I was pretty sure that nothing would care if I did upgrade the schema, but if I could avoid it until I actually needed, I would probably hold off. We don't run any apps other than Windows clients that are aware of AD so fortunately it's very low risk to upgrade the schema. – Knox Sep 11 '10 at 0:50

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