Re: [Qemu-devel] [RFC] More robust migration

[Paul Brook <paul@codesourcery.com>]

On Friday 20 February 2009, Jamie Lokier wrote:
> Paul Brook wrote:
> > I suspect that in practice live migration of a VM between different qemu
> > versions ends up comparable to in-place live kernel upgrades. i.e. it
> > takes an awful lot of work and care to make it happen, and in practice
> > isn't going to happen for any particularly useful span of versions.
>
> On the other hand, stored snapshots of guests which are ready to run
> in a particular state are quite useful.  I'm under the impression the
> migration code is/will be useful for storing snapshots of system (not
> disk) state too.  Is that right?

I don't think there's any real difference between snapshotting and migration 
in this case. It's basically the same code.

I'm not saying it's a useless feature, just that it's very extremely to do 
reliably, and for that reason unlikely to happen. An unreliable 
implementation (i.e. one that claims to migrate/snapshot, then breaks some of 
the time) is IMHO worse than nothing.

Paul