Live Migration in Bare-Metal Clouds

Abstract

Live migration allows a running operating system (OS) to be moved to another physical machine with negligible downtime. Unfortunately, live migration is not supported in bare-metal clouds, which lease physical machines rather than virtual machines to offer maximum hardware performance. Since bare-metal clouds have no virtualization software, implementing live migration is difficult. Previous studies have proposed OS-level live migration; however, to prevent user intervention and broaden OS choices, live migration should be OS-independent. In addition, the overhead of live migration mechanisms should be as low as possible. This paper introduces BLMVisor, a live migration scheme for bare-metal clouds. To achieve OS-independent and lightweight live migration, BLMVisor utilizes a very thin hypervisor that exposes physical hardware devices to the guest OS directly rather than virtualizing the devices. The hypervisor captures, transfers, and reconstructs physical device states by monitoring access from the guest OS and controlling the physical devices with effective techniques. To minimize performance degradation, the hypervisor is mostly idle after completing the live migration. A performance evaluation confirmed that the OS performance with BLMVisor is comparable to that of a bare-metal machine.