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Re: [libvirt] snapshots += domain description?


to refresh this old question again:

Snapshots are a great feature, but I encountered a problem with Qemu/KVM: The 
snapshot information does not include the domain description, which breaks 
the following work-flow:
1. create and start domain with RAM=x1, CPU=y1, ...
2. take snapshot
3. shutdown domain
4. edit domain to RAM=x2, CPU=y2, ...
5. start domain and restore previous snapshot

Qemu will start the domain, but will fail to load the saved RAM state:
> qemu: warning: error while loading state for instance 0x0 of device 'ram'

For comparison, VMWare also includes the configuration in the snapshot data 
(see the *.vmsn file), so on restore the right configuration and state of 
mass storage and RAM are restored.

I think the domain XML should be included with the snapshot data, so restoring 
the exact machine is possible. On restore there would be two cases, when 
restoring a live vm:
1. when the already running qemu/kvm-process is compatible with the VM to be 
restored, reuse the running process and issue the loadvm (or what ever).
2. if they are incompatible, kill the running kvm process and start a new one 
with the right setup to load the VM state.

Is someone working on fixing the problem or are there any plans to fix that?

Philipp Hahn           Open Source Software Engineer      hahn univention de
Univention GmbH        Linux for Your Business        fon: +49 421 22 232- 0
Mary-Somerville-Str.1  28359 Bremen                   fax: +49 421 22 232-99
** Besuchen Sie uns auf der CeBIT in Hannover **
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