Netbus: A Transparent Mechanism for Remote Device Access in Virtualized Systems

Abstract

Efficient and seamless access to local as well as remote devices is a desirable property in multiple settings, including blade-servers, datacenters, enterprises, and even in home-based, personal computing environments. New virtualization technologies developed for PC and server platforms are now making it possible to implement remote device access at a level of abstraction transparent to operating systems and their device drivers. This paper presents a new mechanism for transparent device remoting, resulting in a hypervisor-level abstraction termed Netbus. The Netbus software solution provides both (1) efficient and reliable access to networked devices, and (2) remote access to devices not directly attached to networks, an example being a disk locally present on a bladeserver node. Netbus-based device remoting also supports virtual device migration, device hotswapping and efficient device sharing. A Xen-based prototype implementation of Netbus demonstrates transparent device remoting for block and for USB devices, for both bulk and isochronous USB access methods. Within the same administrative domain, seamless access to these devices is maintained during VM migration and during device hotswapping. Experimental evaluations with microbenchmarks and with representative server applications exhibit comparable performance for Netbus-based remote vs. local devices.