Kernel Mechanisms for Supporting Differentiated Services and Content-Aware Request Distribution in Web Clusters Providing Multiple Services

In this paper, we have designed and implemented a kernel-level Web-based QoS (WQoS) mechanism that could efficiently support differentiated services when serving multiple diverse types of Web requests in a cluster-based Web server system. Our mechanism is implemented at kernel level to effectively reduce the number of protection domain switches and data copying between kernel space and user space to accelerate response time. We also use a new content-aware request distribution policy to dispatch requests efficiently in Web clusters providing multiple types of services. Experimental results demonstrate that the Web cluster with our proposed WQoS mechanism can not only efficiently serve multiple types of service requests but also ensure that all requests with high priority can conform to Service Level Agreement (SLA) by dropping acceptable percentage of requests with minor importance during system overload.