[PVE-User] qcow2 "snapshot": are they feasible/planned?

Damiano Verzulli damiano at verzulli.it
Tue Jan 3 09:54:16 CET 2012

Hash: SHA1

Il 03/01/2012 09:19, Dietmar Maurer ha scritto:
>> 	I'm referring to QCOW-snapshotting, and _NOT_ LVM snapshotting, as
>> they are two _very_ different features: I want to be able to snapshot a VM
>> without shutdown down it (a few-seconds "stop" could be ok) being sure that all
>> the state of the VM (memory and filehandles included) will be saved.
> Why do you need that - for backup?

I'm aware that backup, strictly speaking, refer to "storage" (and so,
LVM-like solutions are OK). I'm also aware that the proper way to backup a
DB (like MySQL) is to "dump" its content and store it somewhere. But
creating dumps as well ad recovering from them in case of disaster can be
very time-consuming.

- From my point of view (am I wrong?) is much better to "stop" the machine
for a few seconds, "snapshot everything", "un-stop" the machine.

BTW: maybe it's interesting to know that _NONE_ of the
virtual-infrastructure-environment I tested, clearly support QCOW-snapshot;
most of them, as well as proxmox, rely on "storage-snapshot". So it seems
that the only way I have, as of today, is via CLI on top of libvirt.

Last (but not least), it's hard to "push" for a FOSS-solution when there's
an (important) feature that is offered by well-known proprietary solutions,
even the free (as in beer) one, and not by FOSS-ones :-(

>> 	I saw that requirements for QCOW2-snapshot are met by proxmox: KVM
>> support and QCOW as storage backend. So it seems that the only things that is
>> missing is some "web interface".
>> 	Will proxmox support such a feature?
> AFAIK you can create such snapshots using the monitor - but we have no api for that.

I tried to exec the "savevm" command from the monitor but... something went
wrong as I lost the connection between the monitor and the VM. I suppose
there are some issues regarding the kernel version and related KVM support
(BTW: I made tests with proxmox 1.9).


- -- 
Damiano Verzulli
e-mail: damiano at verzulli.it
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