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 more risk for unexpected results there will be. 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 the application that allows them to synchronize their Pocket PC, BlackBerry, or Palm device no longer works. If the ability to fax from the desktop suddenly disappears, instant messaging vanishes, or they can't access email from an Internet caf , the Exchange administrator can expect emails with a lot of capital letters in them. Many companies have integrated voicemail with Exchange so that users simply click on a voicemail to listen to it, and changes to this functionality can harm the business processes of the company. New antispam software can inadvertently block messages from key customers, if they contain a word such as sale or act now .

If the organization already has Active Directory in place and is on Exchange 2000 Server, 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 Exchange 2000 might well use the existing server hardware and perform in-place upgrades, or in the case of an upgrade from Exchange 5.5, it may 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 may not be needed, but applications testing should still take place.