Abstract
Internet service providers (ISPs) usually use several server pools to host different web applications, to ensure smooth system management and minimum interference between applications. The workload demand in each of the pools can vary dramatically due to a number of factors, including timing and the types of the hosted applications. Therefore, it is desirable that servers should be able to switch between pools to optimise resource usage and maximise company revenue. Internet applications can be modelled as multi-tier queueing networks, with each network station corresponding to each application tier. The advantage of using an analytical model is that performance metrics can be easily computed, and potential system bottlenecks can be identified without running the actual system. In this paper, an analytical model is used to assist dynamic resource allocation in server pools. In addition, an admission control scheme is also used to deal with system overloading. Performance evaluation is conducted via simulation and the experimental results show the benefits of our approach for various workload scenarios.