4.8 Concluding Remarks

The principle concepts of performance engineering are presented in this chapter. A motivating example is described involving the planning, development, and implementation of a call center application. Five examples of how performance considerations should be included in the analysis, design, operation, and evolution of a system are presented. The main issue in performance engineering is how to guarantee that a system will meet its performance goals. The steps required to carry out a performance engineering effort are described. A central issue in the methodology are the models needed to represent workload and the performance of a system. The basic steps of a practical performance engineering methodology include the following.

• Specify the system performance goals.

• Understand the current environment.

• Perform a workload characterization and generate a workload model.

• Develop a performance model.

• Verify and validate the system model, which is composed of the workload and performance models.

• Forecast workload growth.

• Use the system model to analyze the performance of different system architectures and various workload scenarios.

• Select the best alternative (based on the performance model predictions) that presents the best cost-performance relation while satisfying the service levels specified.