A Virtual Machine Migration System Based on a CPU Emulator

Migration of virtual computing environments is a useful mechanism for advanced management of servers and utilization of a uniform computing environment on different machines. There have been a number of studies on migration of virtual computing environments based on virtual machine monitors (e.g., VMware) or language-level virtual machines (e.g., Java). However, migration systems based on a CPU emulator have not received much attention and their viability in a practical setting is not clear. In this paper, we describe Quasar, a virtual machine (VM) migration system implemented on top of the QEMU CPU emulator. Quasar can migrate a whole operating system between physical machines whose architectures are different (e.g., between an x86 machine and a PowerPC machine). Quasar provides a virtual networking facility, which allows migrating VMs to continue communication without disconnecting sockets for migration. Quasar also provides a staged migration function to reduce the downtime of migrating VMs. We have examined the viability of Quasar through experiments, in which Quasar was compared with Xen, SBUML, and UML. The experiments assessed the performance of virtual server hosting, the sizes of the files that represent VMs, and the amount of downtime for VM migration.