Scalable virtual machine deployment using VM image caches

Abstract

In IaaS clouds, VM startup times are frequently perceived as slow, negatively impacting both dynamic scaling of web applications and the startup of high-performance computing applications consisting of many VM nodes. A significant part of the startup time is due to the large transfers of VM image content from a storage node to the actual compute nodes, even when copy-on-write schemes are used. We have observed that only a tiny part of the VM image is needed for the VM to be able to start up. Based on this observation, we propose using small caches for VM images to overcome the VM startup bottlenecks. We have implemented such caches as an extension to KVM/QEMU. Our evaluation with up to 64 VMs shows that using our caches reduces the time needed for simultaneous VM startups to the one of a single VM.