Trace-driven simulation of document caching strategies for Internet Web servers

Given the continued growth of the World-Wide Web, performance of Web servers is becoming increasingly important. File caching can be used to reduce the time that it takes a Web server to respond to client requests, by storing the most popular files in the main memory of the Web server, and by reducing the volume of data that must be transferred between secondary storage and the Web server. In this paper, we use trace-driven simulation to evaluate the effects of various replacement, threshold, and partitioning policies on the performance of a Web server. The workload traces for the simulations come from Web server access logs, from six different Internet Web servers. The traces represent three different orders of magnitude in server activity and two different orders of magnitude in time duration. The results from our simulation study show that frequency-based caching strategies, using a variation of the Least Frequently Used (LFU) replacement policy, perform the best for the Web server workload traces considered. Thresholding policies and cache partitioning policies for Internet Web servers do not appear to be effective.