Migrating from Active Directory 2000/2003 to Active Directory 2008 : Big Bang Migration

The prerequisites are as follows:

• The operating system on the domain controllers is Windows Server 2003 SP1 or higher.

• The domain controller hardware exceeds the Windows 2008 requirements and all software is compatible with Windows 2008, including antivirus software and drivers.

• There is enough disk space free to perform the operating system and Active Directory upgrade. Specifically, verify that your free space is at least twice the size of your Active Directory database plus the minimum 8GB needed to install the operating system.

• The upgrade from 32-bit goes to 32-bit, and 64-bit goes to 64-bit as an in-place upgrade from 32-bit Windows to 64-bit Windows is not supported.

• The current domain functional level is Windows 2000 Native or Windows Server 2003. You cannot upgrade directly from Windows NT 4.0, Windows 2000 Mixed, or Windows Server 2003 interim domain functional levels.

Often, upgrading any given server can be a project in itself. The stand-alone member servers in an environment are often the workhorses of the network, loaded with a myriad of different applications and critical tools. Performing an upgrade on these servers would be simple if they were used only for file or print duties and if their hardware systems were all up to date. Because this is not always the case, it is important to detail the specifics of each server that is marked for migration.

Verifying Hardware Compatibility

It is critical to test the hardware compatibility of any server that will be directly upgraded to Windows 2008. The middle of the installation process is not the most ideal time to be notified of problems with compatibility between older system components and the drivers required for Windows Server 2008. Subsequently, the hardware in a server should be verified for Windows 2008 on the manufacturer’s website or on Microsoft’s Hardware Compatibility List (HCL), currently located at www.microsoft.com/whdc/hcl.

Microsoft suggests minimum hardware levels on which Windows 2008 will run, but it is highly recommended that you install the OS on systems of a much higher caliber because these recommendations do not take into account any application loads, domain controller duties, and so on. The following is a list of Microsoft’s minimum (and recommended) hardware levels for Windows 2008:

• 1GHz x86 or 1.4GHz x64 processor (2GHz or faster)

• 512MB of RAM (2GB of RAM or more)

• 20–30GB free disk space

That said, it cannot be stressed enough that it is almost always recommended that you exceed these levels to provide for a robust computing environment.

Verifying Application Readiness

Nothing ruins a migration process like discovering a mission-critical application is not certified to run in Active Directory 2008 mode. Subsequently, it is very important to identify and list all applications in an environment that will be required in the new environment. Typically only applications that leverage Active Directory schema need to be checked and tested. Standalone applications that do not query Active Directory at all typically have no impact whether the organization is running one version of AD or another.

Backing Up and Creating a Recovery Process

It is critical that a migration does not cause more harm than good to an environment. Subsequently, we cannot stress enough that a good backup system is essential for quick recovery in the event of upgrade failure. Often, especially with the in-place upgrade scenario, a full system backup might be the only way to recover; consequently, it is very important to detail fallback steps in the event of problems. The backup should include the files and the System State.

Virtual Domain Controller Rollback Option

It is always good to have several fallback options, in case one of the options is unsuccessful. Another option to consider, in addition to a full backup, is to create a virtual domain controller. Using a virtual server platform such as Hyper-V or VMware Server, you can create a domain controller for little or no cost.

A virtual machine is created on the host, which can be an existing installation or even on a desktop with Virtual PC or VMware Workstation. This virtual machine is then joined to the domain and promoted to be a global catalog server.

Prior to the upgrade, the virtual global catalog server is shut down. Backup copies of the virtual server files can even be made for safekeeping.

In the event of a major failure in the upgrade process, the virtual global catalog server can be used to rebuild the domain. If the upgrade is successful, the virtual sever can either be turned back on and demoted, or simply be deleted and cleaned from the domain.

Performing an Upgrade on a Single Domain Controller Server

After all various considerations regarding applications and hardware compatibility have been thoroughly validated, a stand-alone server can be upgraded.

The health of the domain controllers should be verified prior to upgrading the domain controllers. In particular, the Domain Controller Diagnostics (DCDIAG) utility should be run and any errors fixed before the upgrade. The Windows Server DCDIAG utility is part of the Support Tools, which can be found on the installation media under \support\tools\. The Support Tools are installed via an MSI package named SUPTOOLS.MSI. After installing the tools, the DCDIAG utility can be run. Verify that all tests passed.

The Active Directory Domain Services forest and the domain need to be prepared prior to the upgrade. This installs the schema updates that are new to Windows 2008 Active Directory. The following steps should be run on the Flexible Single Master Operations (FSMO) role holder, specifically the infrastructure master role holder. In a small environment or a single domain, all these roles are typically on the same domain controller. To prepare the forest and domain, execute the following steps on the domain controller with the roles:

Now that the schema updates have been installed and the domain preparation is done, the domain is ready to be upgraded. Follow these steps to upgrade:

1.	Insert the Windows Server 2008 DVD into the DVD drive of the server to be upgraded. Note Be sure to use the appropriate media for the operating system of the domain controller, specifically 32-bit or 64-bit. If you have Windows 2003 32-bit, you cannot do an in-place upgrade to x64-bit Windows 2008. And an x64-bit version cannot be changed to a 32-bit version of the operating system. Only 32-bit to 32-bit, or 64-bit to 64-bit upgrades are allowed.
2.	The Install Windows page should appear automatically. If not, choose Start, Run and then type d:\Setup, where d: is the drive letter for the DVD drive.
3.	Click Install Now.
4.	Click the large Go Online to Get the Latest Updates button. This ensures that the installation has the latest information for the upgrade.
5.	Depending on your license rights, enter your product key if prompted and click Next
6.	Select I Accept This Agreement on the License page, and click Next to continue.
7.	Click the large Upgrade button.
8.	Review the compatibility report and verify that all issues have been addressed. Click Next to continue.
9.	The system then copies files and reboots as a Windows 2008 server, continuing the upgrade process. After all files are copied, the system is then upgraded to a fully functional install of Windows 2008 (see Figure 1) and will then reboot again. All this can take some time to complete. Figure 1. Big Bang upgrade.
10.	After the final reboot, the domain controller will be at the familiar Ctrl+Alt+Del screen. After logon, the domain controller will open to the Server Manager console, as shown in Figure 2. The domain controller upgrade is complete. Figure 2. Server Manager console after upgrade.

The upgrade process shown in steps 1 through 10 is then repeated for each of the remaining Windows Server domain controllers.