โ Scribed by Kumar, Sanjay; Schwan, Karsten
No coin nor oath required. For personal study only.
Efficient and seamless access to I/O devices during VM migration coupled with the ability to dynamically change the mappings of virtual to physical devices are required in multiple settings, including blade-servers, datacenters, and even in home-based personal computing environments. This paper develops a general solution for these problems, at a level of abstraction transparent to guest VMs and their device drivers. A key part of this solution is a novel VMMlevel abstraction that transparently handles pending I/O transactions, termed Netchannel. Netchannel provides for (1) virtual device migration and device hot-swapping for networked as well as locally attached devices, and (2) remote access to devices not directly attached to networks via transparent device remoting, an example being a disk locally present on a bladeserver node. A Xen-based prototype of Netchannel demonstrates these capabilities 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 live VM migration and during device hotswapping. Experimental evaluations with micro-benchmarks and with representative server applications exhibit comparable performance for Netchannel-based remote vs. local devices.
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