The Importance of Compatibility Testing

The process presented in this chapter is an essential step to take in validating the design for the end-state of the migration or upgrade. The size of the organization and the breadth and scope of the upgrade are important factors to consider in determining the level of testing needed, and whether a full prototype should be conducted.

The differences between a prototype phase and an application testing phase can be dramatic or negligible based on the nature of the upgrade. A prototype phase replicates the end-state as completely as possible, often using the same hardware in the test lab that will be used in the production rollout.

Caution

Application testing can be performed on different hardware with different configurations than the end-state, but be aware that the more differences there are between the testing environment and the actual upgraded environment, the greater the risk for unexpected results. Essentially, you can do an application testing phase without a complete prototype phase, but you shouldn't do a prototype phase without a thorough application testing process.

Most network users don't know or care which server or how many servers perform which task or house which application, but they will be unhappy if an application no longer works after a migration to Windows Server 2003. If the organization already has Active Directory in place and is running Windows 2000 Servers, the risk of application incompatibility is likely to be less than if the organization is moving from an older operating system, such as NT 4 Server, or a competing operating system, such as Novell NetWare. The upgrade from Windows 2000 might well use the existing server hardware and perform inplace upgrades, or in the case of an upgrade from Windows NT4, it might involve implementing entirely new server hardware and new server fault tolerance features, which further change the operating environment. If this is the case, a full prototype phase might not be needed, but applications testing should still take place.