When migrating to an Active Directory based network, you have two primary options: upgrade or new installation....
An upgrade installation is where you install Windows 2000 Server or Windows Server 2003 over an existing Windows NT Server 4.0 installation on each deployed server. New installations use new computer equipment with new installations of the AD host network operating system. The issue of deciding which type if migration to perform is based on more than just hardware availability and budget. In fact, the preferred option of upgrade migration often causes more problems than the new deployment migration option.
When you upgrade systems to a new operating system, much less migrating servers into a Active Directory environment, you must take extra precautions to ensure that the process causes as little production disruption as possible. Upgrade migrations can cause server failures, interruptions in data access, partial to full interruption of the production environment, and operational downtimes. Because of the nature of upgrade migrations, they must often be performed after hours when the network is least in use.
On the other hand, new migration deployments can often be performed during normal business hours. New systems and applications can be deployed and integrated into the existing network with little affect on the current production environment.
No matter what method is used, you must develop a contingency plan to deal with any and all possible problems. So, to keep an upgrade migration under control as much as possible, you need to take the time and make the effort to thoroughly plan out the operation, test the deployment activities, then scheduled and implement the roll out.
James Michael Stewart is a partner and researcher for ITinfopros, a technology-focused writing and training organization.