The type and number of CPUs attached to a Microsoft Exchange Server computer dictate the performance potential for the Microsoft Exchange Server environment. For example, computers based on the Pentium processor offer better performance than computers based on the 486 chip. Also, a 133MHz Pentium performs better than a 100MHz Pentium.
Paging can be viewed as a contention for memory. As with most resources, some contention is tolerable. However, as the contention increases, the system eventually reaches a point where system resources (such as CPU time, bus bandwidth, disk time, and so on) are increasingly passing pages back and forth among the various processes contending for memory. If you were to graph memory contention versus average response times, you would see a smooth line from zero contention up to a point where response times start to increase dramatically. This is often called thrashing. As memory contention increases past the point of thrashing, response times typically increase exponentially. Short periods of thrashing can be acceptable for some environments, but you should try to prevent systems from thrashing, especially during active, mission-critical activities.
When examining the input/output (I/O) subsystem as it relates to performance, there are many factors to consider, such as the type and number of disk controllers, the type of drives installed, and the choices required for fault tolerance. Overall system performance on a Microsoft Exchange Server computer can be dramatically affected by these variables.
It is important to use all available small computer system interface (SCSI) channels and to add more channels, if necessary, to improve performance. Also, the addition of more disk drives can help performance. By adding more drives, you can ensure that the workload is distributed more efficiently.
For optimal network performance, consider adapter types and the type of network medium, such as twisted-pair wire, optical fiber, coaxial cable, and so on. To optimize performance you can: install a high-performance network adapter card in the server; use protocols that are necessary and keep them to a minimum; use multiple network cards; and segment the LAN, if appropriate. Network adapters can provide varying levels of performance. The characteristics of an adapter that can most affect performance involve the bus type, bus width, and the amount of onboard memory on the adapter.