The Internet is undergoing substantial changes from acommunication and browsing infrastructure to a medium for conducting business and services. These changes require that Web servers should support the preferential services such as those in E-commerce and also achieve good fairness among different types of requests. In this paper, some integrated schemes of request dispatching and selecting for Web server clusters is provided, with the goal of achieving load balance and meeting the requirements of both WebQoS and fairness. The stochastic high level Petri net (SHLPN) models for them are given. To cope with the well-known state space explosion problem, this paper a novel approximate analysis technique is proposed, which can significantly reduce the complexity of the model solution. Moreover, the numerical results of the performance analysis for those schemes are presented, and the best one among them is recommended that is suited to the preferential services and can achieve high system performance for Web server clusters.%Internet的服务模式正由传统的通信与信息浏览向电子交易与服务转变,这就要求WWW服务器既支持电子商务类具有优先级的请求,同时也要维护各类Web应用的公平性.以实现系统负载均衡和满足不同请求的WebQoS需求及公平性为目标,讨论并提出了并行WWW服务器集群系统HTTP请求分配和选择的综合方案,并提供了这些方案的随机高级Petri网模型.为解决模型状态空间爆炸问题,还提出了一种可以显著简化模型求解复杂性的近似性能分析技术;给出了综合方案的数值分析结果和性能评价,建议了适合电子商务类应用的、实现高性能集群系统的综合方案.
展开▼
