Provisioning of virtual environments for wide area desktop grids through redirect-on-write distributed file system

We describe and evaluate a thin client solution for desktop grid computing based on virtual machine appliances whose images are fetched on-demand and on a per-block basis over wide-area networks. The approach uses a distributed file system redirection mechanism which enables the use of unmodified NFS clients/servers and local buffering of file system modifications during the appliances lifetime. The file system redirection technique is achieved through user-level proxies, and can be integrated with virtual private network overlays to provide transparent access to image servers even if they are behind firewalls. We have implemented and evaluated a prototype system which allows thin client diskless appliances to boot over a proxy VM bringing on-demand only a small fraction of the appliance image (16 MB out of WOMB) and showing low runtime overhead for CPU-intensive applications. The paper also presents decentralized mechanisms to support seamless image version upgrades.