- 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
5.9 Cost/Performance Analysis
Once the performance model is built and solved and a cost model developed, various analyses can be made regarding cost-performance tradeoffs. The performance model and cost models can be used to assess various scenarios and configurations. Some example scenarios are, \Should we mirror the Web server to balance the load, cut down on network traffic, and improve performance?" \Should we replace the existing Web server with a faster one?" \Should we move from a two-tier C/S architecture to a three-tier one?" For each scenario, we can predict what the performance of each basic component of the global workload will be and what the costs are for the scenario.
The comparison of the various scenarios yields a configuration plan, an investment plan, and a personnel plan. The configuration plan specifies which upgrades should be made to existing hardware and software platforms and which changes in network topology and system architecture should be undertaken. The investment plan specifies a timeline for investing in the necessary upgrades. The personnel plan determines what changes in the support personnel size and structure must be made in order to accommodate changes in the system.
Some people favor the exclusive use of Return on Investment (ROI) analyses to assess the payback of migrating to a C/S system. These analyses have the drawback of looking only at the economic aspect of the issue. Other people decide to invest in client/server systems because they see them as a necessary ingredient of a company's business strategy, an enabling factor to improve customer service and product quality, and to shorten time to market of new products.