p-Jigsaw: A cluster-based Web server with cooperative caching support

Abstract

Clustering provides a viable approach to building scalable Web systems with increased computing power and abundant storage space for data and contents. In this paper, we present a pure-Java-based parallel Web server system, p-Jigsaw, which operates on a cluster and uses the technique of cooperative caching to achieve high performance. We introduce the design of an in-memory cache layer, called Global Object Space (GOS), for dynamic caching of frequently requested Web objects. The GOS provides a unified view of cluster-wide memory resources for achieving location-transparent Web object accesses. The GOS relies on cooperative caching to minimize disk accesses. A requested Web object can be fetched from a server node's local cache or a peer node's local cache, with the disk serving only as the last resort. A prototype system based on the W3C Jigsaw server has been implemented on a 16-node PC cluster. Three cluster-aware cache replacement algorithms were tested and evaluated. The benchmark results show good speedups with a real-life access log, proving that cooperative caching can have significant positive impacts on the performance of cluster-based parallel Web servers. Copyright © 2003 John Wiley & Sons, Ltd.