Virtual I/O scheduler: A scheduler of schedulers for performance virtualization

Abstract

Virtualized storage systems are required to service concurrently executing workloads, with potentially diverse data delivery requirements, that are running under multiple operating systems. Although a number of algorithms have been developed for I/O performance virtualization among operating system (OS) instances and their applications, none results in absolute performance virtualization. By absolute performance virtualization we mean that the performance experienced by applications of one operating system does not suffer due to variations in the I/O request stream characteristics of applications of other operating systems. Key requirements of I/O performance virtualization are fairness and performance isolation. In this paper, we present a novel virtual I/O scheduler (VIOS) that provides absolute performance virtualization by being fair in sharing I/O system resources among operating systems and their applications, and provides performance isolation in the face of variations in the characteristics of I/O streams. The VIOS controls the coarse grain allocation of disk time to the different operating system instances and is OS independent; optionally, a set of OS-dependent schedulers may determine the fine-grain interleaving of requests from the corresponding operating systems to the storage system. Copyright © 2007 ACM.