Predicting and Evaluating Performance Through TCA

TCA is greatly valuable for evaluating existing systems and gauging the improvement caused by changes in code or upgrades in hardware. By changing the parameters within an Excel spreadsheet, projections can easily be made. By running TCA evaluations against old and new versions of software, as illustrated in the Chapter 9 Real World Example Shop.Microsoft.com, changes are validated in a measurable way. TCA is a significant improvement over completing an entire system, including both hardware and software, and then attempting to make improvements to meet requirements after the fact. However, due to its dependence on the actual or projected data and system responses, it is a somewhat reactive method of evaluating performance.

When the overall architecture of a server system requires multiple changes to improve performance, a company s existing TCA criteria may not be designed to take all of these elements into consideration.

What about a new business launching a new Web service? In the last chapter, we discussed the need to have real user data in order to complete the TCA experiment. In addition, validating the impact of more bandwidth, processor capacity, or other physical improvements to the system can be expensive because those resources must be physically present. The cost of having hardware for testing purposes is often hard to justify, especially when the system being tested is not yet generating revenue.