Re: Migrating Vm's from one machine to another...and back

[Chris Lalancette <clalance@redhat.com>]

Jean-Pierre Dion wrote:
> Hi,
> 
> I made some VM migrations between several machines
> (Intel-Intel and Intel-AMD) and when one VM has been
> migrated onto a second machine, I cannot put it
> back on the first one. I talked with Laurent and it
> seems that there is no way (or no obvious one)
> to do that.
> 
> This could be useful when doing some tasks (load
> balancing...).
> 
> Is it an item that is interesting enough to be done ?
> And does anyone have some idea on how to do that ?

Hm, this seems to work for me, in combination with my recently posted "Implement
tcp nowait option" patch.  Basically you start the guest on machine A like
normal.  Then you start the "container" on machine B with the -incoming flags.
Now you migrate the guest over to machine B (I assume you've gotten this far).
Now, you kill the container on machine A (since the running guest is on B now),
and restart it with -incoming.  Now you migrate back from B to A, and it all
works out.

You can actually probably get rid of one of these steps by starting the machine
on machine A in the first place with -S -incoming tcp://0:4444,nowait, and then
running "cont" in the monitor.  In this case, the machine is already running,
and *also* listening for incoming migrate requests.  Now you do exactly the same
on machine B, and you should be able to migrate back and forth between them at will.

Chris Lalancette