> From: Slohm Gadaburi [mailto:[EMAIL PROTECTED]
> On 12/3/07, Uri Lublin <[EMAIL PROTECTED]> wrote:
> > > From: [EMAIL PROTECTED] on behalf of Slohm Gadaburi
> > > I want to use VM Snapshots.. But I read QEMU's docs saying
> > > that one must use qcow2 file image for that. The problem is that
> > > My Ubuntu 7.04-based qemu-img (v 0.8.2) has only qcow...
> >
> > With qemu v 0.8.2 one can save/load the VM state into/from a file (using
> > monitor commands savevm/loadvm)
> > This is not a "real" VM snapshot, as the disk image changes when the guest
> > runs, but it works fairly well.
>
> Can you please elaborate on that ?
> Can I use savevm to save the current running state of my machine, and
> later restore the exact state using loadvm (with qcow) ?
> Let's say I use -snapshot mode, so I am guranteed my image does not
> change... so is this a real VM snapshot ?
Qemu (v 0.8.2) monitor command "savevm" does not save the state of the disk
(your qcow image).
If you stop+savevm+quit, and the next time you run your guest you loadvm+cont,
then you are safe.
If you savevm and continue running the guest, the disk changes and the next
loadvm may fail.
If you use -snapshot, then the snapshot's temporary disk file is part of the
disk state (a part which is not saved), which means
that even "stop, savevm, quit, start, loadvm, cont" may not work correctly. In
other words everything
your guest have written to (local temporary) disk disappears.
Think of a case when you run with -snapshot and download the newly released
DVD-iso of your favorite linux distribution.
Would you expect to find that iso file after savevm/quit/loadvm ?
You'd probably not find it and your snapshot image's file system would be
corrupted.
Think of a case when your guest runs a database server...
I hope that helps.
Uri.
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