WEB SERVER PERFORMANCE-MEASUREMENT AND MODELING TECHNIQUES

The popularity of the Internet, and the usage of the world wide web in particular, has grown rapidly in recent years. Thousands of companies have deployed Web servers and their usage rates have increased dramat ically. Our research has focused on measuring, analyzing and evaluatin g the performance of Internet and Intranet Web servers with a goal of creating capacity planning models. We have created layered queuing mod els (LQMs) and demonstrated their superiority to traditional queuing n etwork models since they incorporate layered resource demands. Along t he way we built a tool framework that enables us to collect and analyz e the empirical data necessary to accomplish our goals. This paper des cribes the custom instrumentation we developed and deployed to collect workload metrics and model parameters from large-scale, commercial In ternet and Intranet Web servers. We discuss the measurement issues per taining to model parametrization and validation. We describe an object -oriented tool framework that significantly improves the productivity of analyzing the nearly 100 GBs of measurements collected during this workload study interval. Finally, we describe the LQM we developed to estimate client response time at a Web server. The model predicts the impact on server and client response times as a function of network to pology and Web server pool size. We also use it to consider the conseq uences of server system configuration changes such as decreasing the H TTP object cache size. (C) 1998 Published by Elsevier Science B.V. All rights reserved.