Re: [Qemu-devel] [RFC]VM live snapshot proposal

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Huangpeng (Peter) (peter.huangpeng@huawei.com) wrote:
> > > I think this is different in the same way that block-backup and
> > > block-mirror are different.  Huangpeng's proposal would let you make a
> > > consistent snapshot of disks and RAM.
> > 
> > Right. Though the point isn't about consistency (doing the disk snapshot when
> > memory has converged would be consistent as well), but about having the
> > snapshot semantically right at the time when the monitor command is issued
> > instead of only starting it then and being consistent at the point of completion.
> > 
> > This is indeed like pre/post-copy live migration, and probably both options have
> > their uses. I would suggest starting with the easy one, and adding the
> > post-copy feature on top.
> > 
> 
> Good suggestion, The latest patches of post-copy seems updated 2 years ago.
> https://github.com/yamahata/qemu

I'm working on post-copy at the moment, using Andrea's kernel code,
using bits of Yamahata's code base as well; hopefully it won't
be too long until we have something to post.

> One question:
> Can post-copy fallback if exceptions happen during post-copy?

What do you mean by 'exceptions' here?  Generally postcopy can't fall
back to precopy because once you're in postcopy mode the state
is split between the two machines.

Dave
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK