If you are looking for Active Directory scalability information for Windows Server 2003 or Windows Server 2008, you should check out the Active Directory Maximum Limits (http://technet.microsoft.com/en-us/library/cc756101.aspx) document. This may answer some of your questions, or at least give you some warnings about the recommended maximum number of domain controllers in a domain, maximum number of users supported by NTDS.DIT (Active Directory database), and recommended maximum number of users in a group. See Active Directory scalability for information on the scale limitations of Active Directory.

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