In addition to determining what capacity you need today, assess what capacity you need in the future, within a time frame that you can plan for. Typically, a growth time line is in the range of 12 to 18 months. Growth expectations and changes in usage characteristics are factors that you need to take into account to accommodate growth.
As the number of users and messages increase, you should outline successful guidelines for capacity planning. You need to plan for increases in message traffic for the various servers, a larger volume of users, larger mailbox sizes, more calendar appointments, and so forth. As growth occurs in the user population, usage characteristics change over time. Your deployment goals (and therefore deployment design) must respond accordingly to be viable into the future.
Ideally, you should design your architecture to easily accommodate future growth. For example, use logical names for the Communications Suite services themselves. See Using Logical Service Names for more information. Monitoring the deployment, once it enters its production phase, is also crucial to being able to understand when and by how much a deployment needs to grow.
Total Cost of Ownership (TCO) is another factor that affects capacity planning. This includes choosing the hardware upon which to deploy your Communications Suite. The following table presents some factors to consider as to whether to deploy more smaller hardware systems or fewer larger hardware systems.
Table 2–1 Considerations for Total Cost of Ownership