Xen and the Art of Virtualization

Numerous systems have been designed which use virtualization to subdivide the ample resources of a modern computer. Some require specialized hardware, or cannot support commodity operating sys-tems. Some target 100 % binary compatibility at the expense of performance. Others sacrifice security or functionality for speed. Few offer resource isolation or performance guarantees; most pro-vide only best-effort provisioning, risking denial of service. This paper presents Xen, an x86 virtual machine monitor which allows multiple commodity operating systems to share conventional hardware in a safe and resource managed fashion, but without sac-rificing either performance or functionality. This is achieved by providing an idealized virtual machine abstraction to which oper-ating systems such as Linux, BSD and Windows XP, can be ported with minimal effort. Our design is targeted at hosting up to 100 virtual machine in-stances simultaneously on a modern server. The virtualization ap-proach taken by Xen is extremely efficient: we allow operating sys-tems such as Linux and Windows XP to be hosted simultaneously for a negligible performance overhead — at most a few percent compared with the unvirtualized case. We considerably outperform competing commercial and freely available solutions in a range of microbenchmarks and system-wide tests