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Re: [virt-tools-list] C'ant migrate with virt-manager or virsh



On Thu, Feb 03, 2011 at 12:05:26AM +1100, Justin Clift wrote:
> On 03/02/2011, at 12:02 AM, Daniel P. Berrange wrote:
> > On Wed, Feb 02, 2011 at 11:48:11PM +1100, Justin Clift wrote:
> >> On 02/02/2011, at 11:25 PM, Bruno Lamps wrote:
> >>> I was using fedora 13 (kernel 2.6.32) in one machine and fedora 14 (kernel 2.6.35) in other
> >> 
> >> Ahhh, that might be the problem.  One of the "fundamental" things for migration is that both
> >> the source and destination hosts need to be *exactly* the same kernel version, kvm version, etc.
> > 
> > That's not actually true. The requirement is that the destination must
> > offer the same, or a superset of, the features currently configured for
> > the guest on the source host. This basically means that the KVM version
> > must be the same or newer, and the guest machine type must be available
> > on both hosts.
> > 
> > So migration with a OS family should work across version upgrades, eg
> > from Fedora 13 to 14 to 15 should work in that direction. If you want to
> > migrate in the reverse direction eg, from F15 to F14, you need to take
> > extra care to set the guest machine type to a version that is available
> > on both, and even then some problems may occur depending on how much
> > older the target is than the source.
> > 
> > Migration from Fedora to RHEL or vica-versa will not work at all due
> > to different machine types.
> 
> That's weird.  I've been told (more than once) that things have to match
> exactly.  We don't even support live migration from AMD -> Intel or vice versa.

Don't confuse what is "supported" wrt to a product like RHEL, vs what
is "supported" at a technical level.

You can even migrate AMD -> Intel if you config CPU model suitably,
though some guest apps/kernels may get upset if they don't honour
the declared CPUID and do vendor specific things anyway. Hence why
it isn't supported in something like RHEL, even though it might
work for some use cases

Daniel
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