Improving disk I/O performance in a virtualized system

Desktop virtualization is a general solution for providing users with various working environments on a single physical machine. It is typically based on the virtual machine (VM) technology, which can provide smart sharing policies on the scarce hardware. Compared with native computing environments, however, VM may sacrifice the performance, especially in the I/O subsystem. Although certain methods have been proposed to improve the performance of networking and graphic processing, the performance of disk I/O is almost ignored. In this paper, we propose two methods to reduce the extra overhead on Xen hypervisor at different layers of its disk protocol stack. The experimental results show that on the average 21% of unnecessary CPU cycles can be saved from the Xen hypervisor, and when a high performance disk device is applied in the system, our proposed optimization techniques can improve the overall disk I/O performance by 15.6%-36.6% for all benchmarks used in the experiments. Finally, by evaluating our methods in a practical system of desktop virtualization, user-applications can achieve an improvement of 15.9%-23.7% over the original Xen hypervisor.