What Eucalyptus does is it brings a cloud to an environment that has virtualization, but it doesn't replace virtualization, it just uses whatever virtualization is there. That is what we were really striving for in the open source code. In the open source case, the virtualization technologies are Xen and KVM.

In terms of the commercial data centre, it's been our experience that overwhelmingly, the install base is ESX, VMware's hypervisor, and vSphere. So it became abundantly clear that for our commercial customers, we needed to have a vSphere version of Eucalyptus. What that means is Eucalyptus, like it lays on top of Xen or KVM, will lay on top of vSphere or ESX and turn that virtualized environment into a cloud environment.

How does the image converter work?

One of the problems that we had to solve in developing Eucalyptus for VMware's technologies is an issue with how the virtual machines themselves are stored. You make a virtual machine and you can run it, but when it's not running, you have to store it and the format in which it's stored is different from virtualization technology to virtualization technology.

In particular, the virtualization technologies that VMware uses have a particular image format and it's different than the image format used by Xen, which is also the image format used by Amazon's AWS and the image format used by KVM. So what we had to do was develop a way to convert images from one format to VMware format.