[Xen-users] Re: Hardware differences for 2 xen servers?

[Matthew Palmer <mpalmer@xxxxxxxxxxx>]

On Wed, Jun 21, 2006 at 09:45:54AM +0200, Thorolf Godawa wrote:
> >> My question is, how close to the dom0 servers need to be to run a
> >> domU on either?
> >> Do they need to be the same hardware type.. etc etc etc?
> >Nope, because the dom0 provides a nice hardware abstraction layer. 
> this can be very wrong if you want to use (live)-migration!
> 
> If you just want to start a VM, shutdown it later and restart it on the 
> other server, the two machines can be different.
> 
> But if you want to use such cool things like live-migration for s.th. 
> like loadbalancing or maintanance between two servers they should be the 
> same as possible. That doesn't mean that the destination-server could 
> not have faster/more CPU or more RAM, but the CPU and possibly also the 
> chipset should be the same family!
> 
> Otherwise it can happen during live-migration that on the source-system 
> the CPU is in a status that is not compatible with the 
> destination-system and the VM will crash.

Seriously?  That sounds like a pretty bad failing of live-migration -- I'd
*really* expect live migration to be robust against this sort of thing,
otherwise you'd need to reboot the VM in order to put it onto upgraded
hardware -- and if you've got to reboot it *any* time, then you have to
design your infrastructure to accomodate that, and hence you have the
capability to reboot it without service failure, so you don't really need
live migration after all...

- Matt
A little concerned

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