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Windows Azure actually does this. If the host your virtual machine is on for some reason fails or needs to be replaced your entire VM is migrated to another host. The migration process can take a few minutes but all your data is safe.

My point being. On this topic AWS could learn from Microsoft on how to do cloud.

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The one problem they have is that the majority of their instances include local storage, which would make migration impossible. So the best they can offer is a reboot so the server ends up on another host.

They could potentially do this on their second generation (M3) instances, as well as micro instances if they wanted to. However I'd guess that these instances are just a small percentage of the overall servers used.

> The one problem they have is that the majority of their instances include local storage, which would make migration impossible

True for AWS. Using VMware vSphere then this could be done with a shared nothing migration which moves compute and storage (vMotion + storage vMotion combined).

Xen also does this, but AWS may still be using a very old fork of Xen 2 or 3.

It's unfortunate that there doesn't seem to be a large-scale consumer for the XenServer platform now that Citrix open-sourced the entire thing.

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