7.3 Windows NT/2000 Cluster Technology Fundamentals

Most people were first introduced to cluster technology via Digital Equipment Corporation's (now Compaq) Open VMS Cluster. Also known as a VAXCluster, this technology was introduced around 1984 and revolutionized the way we view computer systems. The VAXCluster (now called an OpenVMS Cluster) provides for a collection of systems to be connected to shared devices, and all systems can read or write to all of the devices. Two key attributes that many are looking for from a clustered environment is performance and scalability. You expect that, after investing extra money on the hardware and software required to support clusters, you will receivesome additional performance and scalability benefits such as parallel processing capabilities, I/O shipping, or other techniques that can be gained from a group of systems operating as one. In some environments such as UNIX or OpenVMS, this can be a reality. However, the current truth in the Windows 2000 environment is that cluster services do not afford any of the true performance and scalability benefits you may desire. One benefit that Windows NT/2000 clustering can afford is availability. By allowing for applications and services to have failover and resiliency capabilities, clusters provide increased application availability. For applications like Exchange Server, clustering can provide protection from some specific causes of downtime like hardware failures.

The last thing you may expect cluster technology to provide for your system is increased manageability. Manageability can come in many forms. The most useful benefit for a clustered Exchange...