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[libvirt] snapshots and LVM


I've just tested the snapshot function, which seems to work, but for
now, is limited to qcow2 images.

Are there any plans to add LVM based snapshots ?

I know LVM would have some limitations, but, with recent distribs (F13,
RHEL6 at least), as snapshots can be merged back into the original LV, I
think we could have at least some snapshots function.

Basically, the domain could be paused, then, the memory can be dumped in
a separated file (as a virsh save do), then, all LVM based disks (and
qcow2 based) could be snapshoted, then, the domain could be reloaded
from the saved state. (or even just resumed, if the save function don't
destroy it like a virsh save does)

LVM gives some (a lot of ?) performance improvements over qcow2, and I
think snapshots would be a lot faster (on my tests, it takes 4 or 5
minutes to snapshot a simple ubuntu guest on qcow2, and even longer to

There would still be some limitations, like:
- check if lvconvert support merging before we create the snapshots
- size of snapshots are fixed, should libvirt monitor the % used, and
auto-grow when needed ?
- there would be no support for snapshot of snapshot

Any thoughts ?

Regards, Daniel

Daniel Berteaud
Société de Services en Logiciels Libres
Technopôle Montesquieu
Tel : 05 56 64 15 32
Fax : 05 56 64 15 32
Mail: daniel firewall-services com
Web : http://www.firewall-services.com

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