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Chapter 2. Resource Monitoring

2.2. System Performance Monitoring

As stated above, system performance monitoring is normally done in response to a performance prob 

lem. Either the system is running too slowly, or programs (and sometimes even the entire system) fail

to run at all. In either case, performance monitoring is normally done as the first and last steps of a

three step process:

1. Monitoring to identify the nature and scope of the resource shortages that are causing the per 

formance problems

2. The data produced from monitoring is analyzed and a course of action (normally performance

tuning and/or the procurement of additional hardware) is taken to resolve the problem

3. Monitoring to ensure that the performance problem has been resolved

Because of this, performance monitoring tends to be relatively short lived in duration, and more de 

tailed in scope.

Note

System performance monitoring is often an iterative process, with these steps being repeated several

times to arrive at the best possible system performance. The primary reason for this is that system

resources and their utilization tend to be highly interrelated, meaning that often the elimination of one

resource bottleneck uncovers another one.

2.3. Monitoring System Capacity

Monitoring system capacity is done as part of an ongoing capacity planning program. Capacity plan 

ning 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 plan 

ning requires a "big picture" view; 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.

2.4. What to Monitor?

As stated earlier, the resources present in every system are CPU power, bandwidth, memory, and

storage. At first glance, it would seem to be that monitoring would consist of just looking at these four

different things.

Unfortunately, it is not that simple. For example, consider a disk drive. What things might you want

to know about its performance?