Staffers with these skills are critical to building the end-to-end system. They should be involved in developing the initial design and building the test environment, and they should be hands-on in the deployment and validation stages.

The testing phase is often difficult because properly emulating a production Exchange environment within a test lab requires simulating cross-site network connectivity, user load, the influence of adjunct programs such as backup jobs and other factors unique to the specific environment. The closer you can get to a mirrored production environment within the test lab, the fewer issues you will see arise during deployment.

The use of Exchange Server Load Simulator (loadsim) allows an organization to test how a server running Exchange responds to e-mail loads. Having an active loadsim session running while performing fail-over tests is an effective way to test the consistency of replicated data and the way the fail-over software will behave when running under loads that are similar to what you expect to see in production. We have also found hardware-based WAN simulators that can be programmed for various speeds and latencies to be invaluable as both testing and debugging tools.

In testing, you are looking to answer questions such as these:

Does the fail-over software perform as expected on both detection and recovery?