As stated earlier, a great deal of system administration revolves around resources and their efficient use. By balancing various resources against the people and programs that use those resources, you waste less money and make your users as happy as possible. However, this leaves two questions:
What are resources?
And:
How is it possible to know what resources are being used (and to what extent)?
The purpose of this chapter is to enable you to answer these questions by helping you to learn more about resources and how they can be monitored.
Before you can monitor resources, you first have to know what resources there are to monitor. All systems have the following resources available:
CPU power
Bandwidth
Memory
Storage
These resources are covered in more depth in the following chapters. However, for the time being all you need to keep in mind is that these resources have a direct impact on system performance, and therefore, on your users' productivity and happiness.
At its simplest, resource monitoring is nothing more than obtaining information concerning the utilization of one or more system resources.
However, it is rarely this simple. First, one must take into account the resources to be monitored. Then it is necessary to examine each system to be monitored, paying particular attention to each system's situation.
The systems you monitor fall into one of two categories:
The system is currently experiencing performance problems at least part of the time and you would like to improve its performance.
The system is currently running well and you would like it to stay that way.
The first category means you should monitor resources from a system performance perspective, while the second category means you should monitor system resources from a capacity planning perspective.
Because each perspective has its own unique requirements, the following sections explore each category in more depth.