Moving servers from Windows 2000 to Windows Server 2003 is a relatively straightforward process. You will almost certainly continue to use the existing DNS and Active Directory configuration, network services, administrative methods, and so on. Obviously, this reduces considerably the amount of work involved in a network upgrade.
Moving Active Directory from Windows Server 2000 to Windows Server 2003 is a relatively simple task. However, you must take a few steps prior to installation, starting with verifying a backup of the directory, followed by running a directory preparation program (Adprep) a number of times, including once for the forest and again for each domain. The information updated in each of these steps must be replicated to every domain controller (in the forest or domain, respectively), taking a little time, but not much effort.
For more information about Adprep, see Chapter 8.
Renaming Active Directory domains isn't easy
Windows Server 2003 introduces the capability to rename domains, which facilitates reorganizing your Active Directory tree after an upgrade. Even with the domain rename capability, however, this is not a trivial process, and you will want to approach renaming operations cautiously. This capability is available only once all domain controllers in the forest are running Windows Server 2003 and the forest is operating in Windows Server 2003 forest functional level.
Review the servers currently acting as domain controllers, noting domain, Internet Protocol (IP) address, and geographic location. Branch offices require special attention because of replication issues. Identify domain controllers that will act as global catalog and bridgehead servers. You also must determine the order in which you will upgrade domain controllers. The recommended order for upgrading domain controllers from Windows 2000 to Windows Server 2003 is
Use the Active Directory Installation Wizard (Dcpromo) to install Active Directory on a Windows Server 2003–based member server in the forest root domain. This creates the first Windows Server 2003 domain controller in the forest.
Upgrade the operating system on the Windows 2000–based domain controller holding the domain naming master role. If you choose not to upgrade the domain controller, transfer the Domain Naming Master role to a domain controller running Windows Server 2003.
Upgrade the operating system on the Windows 2000–based domain controller holding the PDC Emulator role in each domain, or transfer the roles to Windows Server 2003–based domain controllers.
Upgrade all remaining Windows 2000–based domain controllers to Windows Server 2003.
You also must evaluate the disk partition and available free disk space for upgrading the Active Directory database (Ntds.dit) and extensible storage engine (Esent) log files—free space should be a minimum of 10 percent of the existing size of the Active Directory database and 20 percent of the existing size of the log files (a minimum of 300 megabytes [MB]).
Installing service packs might be required before you upgrade
Before upgrading a Windows 2000 forest and domains by using the Active Directory Preparation Wizard, all Windows 2000 domain controllers within the forest must have Service Pack 1 with QFE 265089 or (perhaps more easily) Service Pack 2 or later. This is necessary to avoid domain data corruption. For more information, see Microsoft Knowledge Base article 331161.
Some of your applications will handle the upgrade to Windows Server 2003 without problem, yet not all of them will. Determining which is which beforehand makes the upgrade process much less traumatic. Some widely used applications, such as Microsoft Exchange 2000 Server, simply won't run on Windows Server 2003—something you wouldn't want to find out in the middle of an upgrade.
Prior to upgrading your servers that run Windows 2000, review the Relnotes.htm in the Docs folder of the Windows Server 2003 product CD for information concerning your applications. You might also want to check the software vendor's Web site for relevant information and obtain the Application Compatibility Toolkit from the Microsoft Web site at http://msdn.microsoft.com/compatibility.
Exchange 2000 Server and Windows Server 2003
You should be aware of a number of critical issues if you are running Exchange 2000 Server and are planning to install Windows Server 2003 domain controllers. Although you can work around all of the issues, you must plan for Windows Server 2003 with Exchange 2000 Server in mind.
Some of the problems and their solutions are simple: Exchange 2000 Server won't run on Windows Server 2003. The solution is easy: Keep enough servers running Windows 2000 to host Exchange 2000 Server, or upgrade to Microsoft Exchange Server 2003.
Others are less straightforward: There are schema incompatibilities between Exchange 2000 Server and Windows Server 2003, which can result in corrupted directory information. Because of issues such as this, a number of hot fixes must be applied, schema differences must be accounted for, and so on.
Prior to installing Windows Server 2003 into a network using Exchange Server 2000, be sure to research the issues and workarounds using the Microsoft Knowledge Base articles on the subject—article number 314649 is a good place to start.