Mechanisms for quality of service in Web clusters

The new generation of Web systems provides more complex services than those related to Web publishing sites. Users are increasingly reliant on the Web for up-to-date personal and business information and services. Web archite ctures able to guarantee the quality of service (QoS) that rules the relati onship between users and Web service providers require a large investment i n new algorithms and systems for dispatching, load balancing, and informati on consistency. In this paper. we consider Web cluster architectures compos ed of multiple back-end server nodes and one front-end dispatcher and we an alyze how to provide differentiated service levels to various classes of us ers. We demonstrate through simulation experiments under realistic workload models that the proposed mechanisms are able to satisfy QoS requirements o f the most valuable users classes, without impacting too negatively on the other users. (C) 2001 Elsevier Science B.V. All rights reserved.