2.3. Monitoring System Capacity

Monitoring system capacity is done as part of an ongoing capacity planning program. Capacity planning uses long-term resource monitoring to determine rates of change in the utilization of system resources. Once these rates of change are known, it becomes possible to conduct more accurate long-term planning regarding the procurement of additional resources.
Monitoring done for capacity planning purposes is different from performance monitoring in two ways:
  • The monitoring is done on a more-or-less continuous basis
  • The monitoring is usually not as detailed
The reason for these differences stems from the goals of a capacity planning program. Capacity planning requires a "big picture" viewpoint; short-term or anomalous resource usage is of little concern. Instead, data is collected over a period of time, making it possible to categorize resource utilization in terms of changes in workload. In more narrowly-defined environments, (where only one application is run, for example) it is possible to model the application's impact on system resources. This can be done with sufficient accuracy to make it possible to determine, for example, the impact of five more customer service representatives running the customer service application during the busiest time of the day.