Defining the Migration Process

Any migration procedure requires a defined procedure that details the reasons for migration, steps involved, fallback precautions , and other important factors that can influence the migration process. When these items have been finalized, the steps toward performing the migration implementation can be accomplished and the performance increases can be realized.

Defining Exchange Server 2003 Objectives

As part of any migration project, establishing project objectives are a critical but often overlooked aspect of a project. Without objectives, it becomes difficult to define whether a project has been successful. Although there are significant improvements between Windows NT 4.0 domains and Windows Server 2003 AD, the ultimate decision to upgrade might be to support Exchange Server 2003. As previously mentioned, Exchange Server 2003 requires a functional Windows 2000/2003 Active Directory implementation for its directory, and this might force an organization to upgrade.

NOTE

Although it is necessary for Exchange 2000/2003 to use an Active Directory forest for directory and authentication purposes, there is one scenario in which an existing NT 4.0 domain can be preserved, if desired or required. Exchange Server 2003 can be installed in a new, separate AD forest, with a manual trust established to the production NT domain. The NT domain accounts can then be granted full mailbox privileges to the Mailbox-enabled user accounts that can be created in the AD domain.

Establishing Migration Project Phases

After the decision has been made to upgrade, a detailed plan of the resources, timeline, scope, and objectives of the project should be outlined. Establishing a project plan, whether ad hoc or professionally drawn up, should be part of any migration plan, to assist in accomplishing the planned objectives in a timely manner with the correct application of resources.

A condensed form of the standard phases for a migration project is detailed as follows :

• Discovery The first portion of a design project should be a discovery, or fact-finding portion. This section focuses on the analysis of the current environment and documentation of the results of the analysis. Current network diagrams, server locations, WAN throughputs, server application dependencies, and all other relevant sections should be detailed as part of the Discovery phase.

• Design The Design portion of a project is a straightforward concept. All key components of the actual migration plan should be documented and key data from the Discovery phase should be used to draw up Design and Migration documents. The project plan itself would normally be drafted during this phase. This is especially true with Windows NT 4.0 because there are significant differences in structure between NT and Windows Server 2003.

• Prototype The Prototype phase of a project involves the essential lab work to test the design assumptions that were made during the Design phase. The ideal prototype would involve a mock production environment that is migrated from Windows NT 4.0 to Windows Server 2003. Step-by-step procedures for migration can also be outlined and produced as deliverables for this phase.

• Pilot The Pilot phase, or Proof-of-Concept phase, involves a production "test" of the migration steps, on a limited scale. For example, a single domain controller could be upgraded to Windows Server 2003 in advance of the migration of all other domain controllers.

• Implementation The Implementation portion of the project is the full-blown migration of network functionality or upgrades to the operating system. This process can be done quickly or slowly over time, depending on the needs of an organization. Make the timeline decisions in the Design phase and incorporate them into the project plan.

• Training and Support Learning the ins and outs of the new functionality that Windows Server 2003 can bring to an environment is essential towards the realization of the increased productivity and reduced administration that the OS can bring to an environment. Consequently, it is important to include a training portion in a migration project, so that the design objectives can be fully realized.

For more detailed information on the project plan phases of a migration, reference Chapter 2, "Planning, Prototyping, Migrating, and Deploying Exchange Server 2003."

In-Place Upgrade Versus New Hardware Migration

Because the underlying operating system kernel is similar between Windows NT 4.0 and Windows Server 2003, the possibility exists to simply upgrade an existing Windows NT Server in place. Depending on the type of hardware currently in use in a Windows NT 4.0 network, this type of migration strategy becomes an option. Often, however, it is more appealing to simply introduce newer systems into an existing environment and retire the current servers from production. This type of technique normally has less impact on current environments and can also support fallback more easily.

Which migration strategy to choose depends on one major factor: the condition of the current hardware environment. If Windows NT 4.0 is taxing the limitations of the hardware in use, it might be preferable to introduce new servers into an environment and retire the old Windows NT 4.0 servers. If, however, the hardware in use for Windows NT 4.0 is newer and more robust, and could conceivably last for another 2 “3 years , it might be easier to perform in-place upgrades of the systems in an environment.

In most cases, a dual approach to migration is taken. Older hardware is replaced by new hardware running Windows Server 2003. Newer Windows NT 4.0 systems are upgraded in place to Windows Server 2003. Consequently, performing an audit of all systems to be migrated and determining which ones will be upgraded and which ones will be retired is an important step in the migration process.

Choosing a Migration Strategy

As with many technology implementations , there are two approaches that can be taken regarding deployment: a quick, "Big-Bang" approach, or a phased, slower approach. The Big-Bang option involves quickly replacing the entire Windows NT 4.0 infrastructure (often over the course of a weekend ) with the new Windows Server 2003 environment. The phased approach involves a slow, server-by-server replacement of Windows NT 4.0. Each approach has its advantages and disadvantages, and there are key factors of Windows Server 2003 to take into account before a decision is made.

Because there are fundamental structural changes between the NT domain structure and Active Directory, the argument of not maintaining two conflicting and redundant environments for long periods of time supports the Big-Bang approach. That said, there are situations in which the phased approach might be more appealing. Larger organizations with a heavy investment in Windows NT 4.0 might determine that a phased approach will help divide the upgrade into manageable components. Other risk-averse organizations might decide to minimize risk through the use of this strategy. Windows Server 2003 easily accommodates both migration options.

Exploring Migration Options

Migration to Windows Server 2003 can be precipitated by one of many factors. In the case of Exchange Server 2003, the necessity of an Active Directory infrastructure in place requires that the infrastructure be upgraded to support it. Other reasons also might justify the upgrade, such as improvements in reliability, scalability, and a lower Total Cost of Ownership (TCO). In any case, an upgrade from NT 4.0 to Windows Server 2003 can be done in several ways.