- Chapter 5 A Step-By-Step Approach to Capacity Planning in Client/Server Systems
- 2 Adequate Capacity
- 3 A Methodology for Capacity Planning in C/S Environments
- 4 Understanding the Environment
- 5 Workload Characterization
- 6 Workload Forecasting
- 7 Performance Modeling and Prediction
- 8 Development of a Cost Model
- 9 Cost/Performance Analysis
- 10 Concluding Remarks
Figure 5.2 illustrates the various steps of a capacity planning methodology for C/S systems. While these steps are essentially the same as those for capacity planning studies of mainframe-based environments, their implementation in a C/S environment is much more complex due to the heterogeneity of hardware and software components involved.
The capacity planning methodology relies on three models: a workload model, a performance model, and a cost model. The workload model captures the resource demands and workload intensity characteristics for each component of a global workload within a representative time frame. The performance model is used to predict the performance of a C/S system as a function of the system description and workload parameters. The outputs of the performance model include response times, throughputs, utilizations of various system resources, and queue lengths. These performance metrics are matched against the service-level agreements to determine if the capacity of the system is adequate. The cost model accounts for software, hardware, telecommunications, and support expenditures.
The following sections discuss in greater detail what is involved in each of the steps of the methodology depicted in Fig. 5.2. We will use the C/S of Fig. 5.3 to illustrate all phases of the capacity planning methodology.
Figure 5.2. A methodology for capacity planning.