[libvirt] RFCv2: virDomainSnapshotCreateXML enhancements

[Philipp Hahn]

Hello Kevin, hello Eric,

On Thursday 11 August 2011 12:00:46 Kevin Wolf wrote:
> Am 11.08.2011 00:08, schrieb Eric Blake:
> > Libvirt currently has a bug in that it only saves <domain>/<uuid> rather
> > than the full domain xml along with a checkpoint - if any devices are
> > hot-plugged (or in the case of offline snapshots, if the domain
> > configuration is changed) after a snapshot but before the revert, then
> > things will most likely blow up due to the differences in devices in use
> > by qemu vs. the devices expected by the snapshot.
>
> Offline snapshot means that it's only a disk snapshot, so I don't think
> there is any problem with changing the hardware configuration before
> restoring it.
>
> Or does libvirt try to provide something like offline checkpoints, where
> restoring would not only restore the disk but also roll back the libvirt
> configuration?

Try to load a VM state with the memory size changed in between and your VM is 
busted; been there, experienced that :-( So it's nice to do a snapshot before 
you play with your virtual hardware configuration and can go back there if 
things go wrong.

For -loadvm to work you have to call kvm with the nearly same command line 
arguments again; what may change you probably know better than me. For I 
thinks it's essential to store the VM consiguration with the snapshot, which 
would be the qemu command line arguments, which is equivalent to libvirts XML 
description.

Sincerely
Philipp
-- 
Philipp Hahn           Open Source Software Engineer      hahn at univention.de
Univention GmbH        Linux for Your Business        fon: +49 421 22 232- 0
Mary-Somerville-Str.1  D-28359 Bremen                 fax: +49 421 22 232-99
                                                   http://www.univention.de/
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