7.8. Concluding Remarks

In this chapter, we learned the concepts of capacity planning and adequate capacity. We saw that capacity planning relies on predictive performance models. These models will be treated in detail in Chapters 8 and 9.

A methodology for capacity planning for e-business sites was presented and illustrated through various examples. For e-business, capacity planning entails three planning activities: business and functional planning, customer behavior planning, and IT resource planning.

Business and functional planning involves characterizing the business and analyzing the functions to be provided by the e-commerce site. Customer behavior planning includes the activities related with understanding how customers interact with the site and building customer behavior models. Finally, IT resource planning deals with the IT resources used to support the e-business and the models used to characterize the workload and predict the performance of the various transactions derived from the execution of e-business functions.

The capacity planning process involves various models. The business model describes the type of business (e.g., B2C e-tailer, C2C auction, and B2C service), the type of product or service delivery (e.g., physical goods, real time digital delivery over the Internet, and digitized music), use of third-party services, market composition, and hours of operation. The business model also includes several quantitative business descriptors (e.g., number of customers, number of items in the catalog, and number of catalog items sold per month per category). These descriptors provide business-related attributes that are important for capacity planning purposes. The functional model describes the functions provided by the e-business site. The customer behavior model describes how users navigate through the site as they use the various e-business functions. The workload model provides a synthetic description of the various transactions that implement the e-business functions. This description includes workload intensity parameters and service demand parameters. Finally, the performance model is a representation of the e-business site that can be used to predict the performance of the site under the workload described by the workload model as well as to answer various what-if questions.