On disk I/O scheduling in virtual machines

Abstract

Disk I/O schedulers are an essential part of most modern op-erating systems, with objectives such as improving disk uti-lization, and achieving better application performance and performance isolation. Current scheduler designs for OSs are based heavily on assumptions made about the latency characteristics of the underlying disk technology like elec-tromechanical disks, flash storage, etc. In virtualized envi-ronments though, with the virtual machine monitor sharing the underlying storage between multiple competing virtual machines, the disk service latency characteristics observed in the VMs turn out to be quite different from the tradition-ally assumed characteristics. This calls for a re-examination of the design of disk I/O schedulers for virtual machines. Recent work on disk I/O scheduling for virtualized environ-ments has focused on inter-VM fairness and the improve-ment of overall disk throughput in the system. In this pa-per, we take a closer look at the impact of virtualization and shared disk usage in virtualized environments on the guest VM-level I/O scheduler, and its ability to continue to en-force isolation and fair utilization of the VM’s share of I/O resources among applications and application components deployed within the VM. 1.