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Active Directory migration: Upgrade vs. restructure

Learn the key considerations every administrator should make before migrating Microsoft Active Directory.

Moving from a Windows NT-based domain to a Windows 2000 Active Directory-based domain brings numerous benefits....

In this tip, I'll focus on how to make decisions about the upgrade process itself.

When moving from NT domains to Active Directory domains, there are two possible methods you can use: upgrading or restructuring. These are two independent activities but they can be combined in sequential order if desired.

Upgrading is the process of moving over to an Active Directory domain while retaining the network roles of servers and the overall network structure. Often called an in-place upgrade, it's a simple upgrade of the PDC and all BDCs from Windows NT to Windows 2000.

Restructuring is the process of starting over, redesigning the network structure and reassigning the server network roles. Often restructuring will result in fewer but larger domains.

Deciding which path to take, or which process to perform first, all depends on your specific situation. But there are a few guidelines to help you make the choice:

If your current domain structure is supporting your work tasks and doesn't seem to involve an inordinate amount of extraneous administration, then upgrading may be preferable. If the current domain structure is not adequate and is the primary motivation for the migration, restructuring is probably preferable.

If you must support the production environment throughout the migration process, upgrading will retain overall network functionality and therefore is preferable. But if you can afford to lose productivity during the migration, restructuring is better. However, restructuring can be performed on a staggered schedule so no significant loss of productivity is noticed.

Generally, migrate the PDC system within a domain first. Windows 2000 offers backwards compatibility for Windows NT BDCs and thus offers a way to mix the domain environments until a complete migration can be accomplished. Also, when multiple domains are involved, migrate account domains before resource domains.

It is important to complete the migration process, whether upgrading or restructuring, before spending considerable efforts in application deployment or group policy management. Otherwise, if significant changes occur afterward, all of the efforts put into these tasks will be lost.

James Michael Stewart is a researcher and writer for Lanwrights, Inc.

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