VMCD: A Virtual Multi-Channel Disk I/O Scheduling Method for Virtual Machines

Abstract

In the era of cloud computing and big data, virtualization is gaining great popularity in storage systems. Since multiple guest virtual machines (DomUs) are running on a single physical device, disk I/O fairness among DomUs and aggregated throughput remain the challenges in virtualized environments. Although several methods have been developed for disk I/O performance virtualization among multiple DomUs, most of them suffer from one or more of the following drawbacks. (1) A fair scheduling mechanism is missing when requests converge together from multiple queues. (2) Existing methods rely on better performance of the underlying storage system such as solid state drive (SSD). (3) Throughput and latency are not considered simultaneously. To address these disadvantages, this paper presents a virtual multi-channel of disk I/O (VMCD) method that can be built on top of an ordinary storage utility, which mitigates the interference among multiple DomUs by using separated virtual channel (V-Channel) and an I/O request queue for each DomU. In our VMCD, several mechanisms are employed to enhance the I/O performance, including a credit allocation mechanism, a global monitoring strategy, and a virtual multi-channel fair scheduling algorithm. The proposed techniques are implemented on the Xen virtual disk and evaluated on Linux guest operating systems. Experiments results show that VMCD increases fairness by 70 percent approximately compared with CFQ and Anticipatory schedulers, by 30 percent approximately compared with Deadline scheduler; and enhances bandwidth utilization by 28 percent approximately compared with CFQ and Anticipatory schedulers, by 37 percent compared with Deadline in the case of three or more virtual DomUs running on the same physical host.