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 architectures able to guarantee the quality of service (QoS) that rules the relationship between users and Web service providers require a large investment in new algorithms and systems for dispatching, load balancing, and information consistency. In this paper. we consider Web cluster architectures composed of multiple back-end server nodes and one front-end dispatcher and we analyze how to provide differentiated service levels to various classes of users. We demonstrate through simulation experiments under realistic workload models that the proposed mechanisms are able to satisfy QoS requirements of the most valuable users classes, without impacting too negatively on the other users. (C) 2001 Elsevier Science B.V. All rights reserved.