xnbd is an interesting choice, if they're using it for the server. In theory it can do live-migration, but the live-migration scheme it uses has (or had, it's

xnbd is an interesting choice, if they're using it for the server. In theory it can do live-migration, but the live-migration scheme it uses has (or had, it's been a while since I looked) a bit of a flaw in that it could lose writes. It'll be doing better than a typical virtual machine because there's no contention on the host side, kernel or IO, and at this point, you've probably got the storage device to yourself so there's no bus contention. The trade-off is shutdown time: they've got to slurp your disc image off to their block store before they can release your node back to the pool.