Validation phase - System Testing - Performance Testing - Utilization

Utilization refers to the usage level of different system resources, such as the server's CPU, memory, network bandwidth and do forth. It is usually measured as a percentage of the maximum available level of the specific resources.

Utilization usually increases proportionally to increasing user load. However, it will top off and remain at a constant when the load continues to build up. If the specific system resource tops off at 100 percent utilization, it is very likely that this resource has become the performance bottleneck of the site. Upgrading the resource with higher capacity would allow greater throughput and lower latency thus better performance. If the measured resource does not top off close to 100 percent utilization, it is probably because one or more of the other system resources have already reached their maximum usage levels. They have become the performance bottleneck of the site.

To locate the bottleneck, there is a need to go through a long and painstaking process of running performance tests against each of the suspected resources, and then verifying if performance is improved by increasing the capacity of the resources. In many cases, performance of the site will start deteriorating to an unacceptable level well before the major system resources, such as CPU and memory, are maximized.