Sanjay Kumar, Sandip Agarwala, Karsten Schwan,
Netbus: A Transparent Mechanism for Remote Device Access in Virtualized Systems
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.