virtualbox.org

I've got a setup where I need to be able to copy VMs from one host to another; I don't need a full live teleport, but I do need saved state to be preserved.

I've tested this some, and every case I've tried works fine - but I'm still somewhat wary, having come from the vmware world where any tiny difference between host hardware or software would result in saved state failing to transfer.

So the question is: Is this something I should expect to work? Do I need to set --synthcpu in order to make this a thing I can rely on? And if I do set --synthcpu, is that likely to cause any problems on its own? Presumably there's some good reason it's not on by default...

You may want to read comment 16 from frank in ticket #9524 about synthcpu.

IMHO, if your project relies on the portability of saved states then it's doomed to eventual failure.

rpmurray wrote:You may want to read comment 16 from frank in ticket #9524 about synthcpu.

Thanks, that was very useful. Marking the option with "experimental" and "requires cpu flags to be set" would have been nice things to have in the documentation...

...But it sounds like this is, overall, not going to be reliable, despite the fact that it's worked perfectly in the cases I've tested. That's rather unfortunate, but I had methods to deal with this issue under vmware, and I can re-implement that under virtualbox. (If you're curious, those methods involved shipping the VMs around in a powered-off state and having a very specific startup sequence to re-create the actual desired state. It's obnoxious to set up and get right, but it did work.)

Out of curiosity, do these same sorts of issues / limitations apply to the live teleport feature?

They normally do not, but doing a teleport means you're going to have the VM running on one CPU then on another, out of the blue. So it could crash the system, yes.