eucalyptus image format, instance-clonning and auto-scaling

Question

I am not familiar with eucalyptus and have question regarding the images, instances, clonning and how I can achieve auto-scaling with eucalyptus. Eucalyptus I believe supports many hypervisors like Xen, Vmware ESXi. So if I create a private cloud using eucalyptus with hybrid hypervisors like Xen, ESXi then in this case what is the image format of the eucalyptus VM image? Is it specific to hypervisors used in building the private cloud? Or is it a specific format of the eucalyptus system which is converted into specific hypervisor format when the vm is selected to run with a node? If so how much time it takes for this task and what technology is used to convert images? How can I clone images in hybrid environment to achieve amazon like instance auto-scale functionality?

Answer 1

Eucalyptus uses the same convention that Amazon's AWS uses, that is, you uses 'root' partitions. The format is raw, that is, there is no real format, just whatever file-system you put onto the partition (ie ext2, ext3 etc ...).

If you want to have your image to be portable across hypervisors and clouds, you will have to ensure that your images will boot correctly across different hypervisors and different kernels. The former means you will have to ensure you have all the drivers needed by they hypervisor, and the latter means that you will have to include all kernel modules needed (typically only the cloud administrator uploads kernels, so you will have to adapt).

Eucalyptus takes care of the internal conversions (for example KVM wants to boot off a disk image, xen off a partition and vmware wants its own format), but it's transparent to the user.

If you are using windows images, you will upload instead full disk, not only partitions: in this case hardware virtualization is required, and you will implicitely use the kernel you have on the disk image. You still have the issue of ensuring the image contains all the drivers needed by the image when running from the virtualized environment.