Fast Software Rejuvenation of Virtual Machine Monitors

As server consolidation using virtual machines (VMs) is carried out, software aging of virtual machine monitors (VMMs) is becoming critical. Since a VMM is fundamental software for running VMs, its performance degradation or crash failure affects all VMs running on top of it. To counteract such software aging, a proactive technique called software rejuvenation has been proposed. A simple example of rejuvenation is to reboot a VMM. However, simply rebooting a VMM is undesirable because that needs rebooting operating systems on all VMs. In this paper, we propose a new technique for fast rejuvenation of VMMs called the warm-VM reboot. The warm-VM reboot enables efficiently rebooting only a VMM by suspending and resuming VMs without saving the memory images to persistent storage. To achieve this, we have developed two mechanisms: on-memory suspend/resume of VMs and quick reload of a VMM. Compared with a normal reboot, the warm-VM reboot reduced the downtime by 74 percent at maximum. It also prevented the performance degradation due to cache misses after the reboot, which was 52 percent in case of a normal reboot. In a cluster environment, the warm-VM reboot achieved higher total throughput than the system using VM migration and a normal reboot.