Alleviating I/O Interference via Caching and Rate-Controlled Prefetching without Degrading Migration Performance

Abstract

The process of migrating a virtual machine and its virtual storage can greatly degrade the performance of other guests and applications running on the same host, including the migrating machine itself. Through experimental evaluation, we investigate the I/O performance degradation imposed by storage migration on co-located machines. We examine naive approaches for mitigating this interference by adjusting host system settings and migration parameters. While effective in some contexts, our analysis demonstrates that performing a migration using these I/O constraining techniques will increase migration latency and limit its ability to converge. Therefore, we present a design and analysis of Storage Migration Offloading, a migration method that reduces I/O interference, maintains lower migration latency, and converges under higher dirty rates. Storage Migration Offloading utilizes a buffer store populated during migration using a dynamic cache policy and rate controlled prefetching. Data is transferred to the destination host from both the buffer and primary disks in a way that minimizes interference on the primary disk while attempting to maintain the desired migration speed.