Impact of server dynamic allocation on the response time for energy-efficient virtualized web clusters

Virtualization has been widely adopted in data centers around the world for improving resource usage efficiency; particularly helping to make these computing environments more energy-efficient. Server virtualization allows for on-demand allocation (using either migration or replication) of virtual machines (VMs), which run the web applications and services, to physical servers. In this paper, we measure and analyze the disruptive impact on the QoS (quality-of-service) provided by the applications, in terms of server-side response time and throughput, during dynamic allocation of virtual machines in a server cluster. The response time of the web applications in the cluster is adopted as our main QoS metric since it is crucial for qualifying the end-user experience. In our experiments, we use Xen as the virtual machine manager and Apache servers for running the web applications. Our results show that VM replication with workload balancing may lead to reduced disruption impact on the QoS measures when compared to VM migration.