In an earlier blog post [March 2, 2009], we discussed why private clouds enjoy only a small subset of the benefits of public clouds. If common API's allowed the same application to transition between a private cloud and a public cloud, we believe application operators could enjoy the full benefits of cloud computing. We referred to this capability as "surge computing" in our Above the Clouds white paper.
Surge computing would allow developers to push just enough (possibly sanitized) data into the cloud to perform a computation and obtain an acceptable result, or seamlessly pull in resources from a public cloud when local capacity is temporarily exceeded. They could even use either the private cloud or the public cloud as a "spare" in the event that one cloud environment becomes unavailable or fails.
One early surge-computing tool available to SaaS developers is Eucalyptus, an open source reimplementation of the Amazon Web Services EC2 APIs. The Eucalyptus software was originally developed at UC Santa Barbara, and Eucalyptus Systems, recently raised $5.5M to provide consulting services and technical support for customers constructing private clouds. Canonical Ltd. announced that Eucalyptus will be the underlying technology used in the Ubuntu Enterprise Cloud, which previewed in the latest version of Ubuntu (9.04 released April 23rd 2009). Finally, companies like RightScale have committed to allowing their customers to register their private Ubuntu Enterprise Clouds and have them managed alongside applications deployed on Amazon EC2 via a single interface (the RightScale dashboard).