Re: [libvirt] RFCv2: virDomainSnapshotCreateXML enhancements

Am 12.08.2011 09:18, schrieb Philipp Hahn: > 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. Yes, I understand this. I was talking about snapshots taken while the VM is shut off, where it's not as clear.

But for consistency it's probably better to do the same with offline and online snapshots, so what libvirt implements (or was it only Eric's plan?) is fine here.