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Dan Williams (Cornell University)

Hani Jamjoom (IBM Watson Research)

Hakim Weatherspoon (Cornell University)

Past Collaborators

Eslam Elnikety (KAUST)

Mohamed Eldehiry (KAUST)

Hai Huang (IBM Watson Research)


Infrastructure-as-a-Service (IaaS) clouds are evolving from offering simple on-demand resources to providing diverse sets of tightly-coupled monolithic services. Like OS kernels of the 1980's and 1990's, these monolithic offerings, albeit rich in features, are significantly constraining users' freedom and control over the underlying---cloud---resources. For example, we are unaware of a true hybrid cloud, where its users can migrate virtual machines freely across clouds. This paper argues for a new type of IaaS cloud, an xCloud, that builds on ideas from extensible OSs to give users the flexibility to install custom cloud extensions, which can address the limitations outlined above. We describe the design space for xClouds, including a practical approach for transforming today's public clouds into xClouds.

Code Release

Code to transform public clouds into xClouds is now available! The release consists of patches for Xen and Blanket drivers for Linux. Begin by downloading the tarball at, and check out the README for instructions of how to run Xen inside your own EC2 instance!


Dan Williams, Hani Jamjoom, and Hakim Weatherspoon. The Xen-Blanket: Virtualize Once, Run Everywhere. In Proceedings of ACM EuroSys, Bern, Switzerland, April 2012.

Dan Williams, Eslam Elnikety, Mohamed Eldehiry, Hani Jamjoom, Hai Huang, and Hakim Weatherspoon. Unshackle the Cloud! In Proceedings of the 3rd USENIX Workshop on Hot Topics in Cloud Computing (HotCloud), Portland, OR, June 2011.