Re: [Qemu-block] [Qemu-devel] storing machine data in qcow images?

[Daniel P . Berrangé]

On Wed, Jun 06, 2018 at 11:14:32AM -0300, Eduardo Habkost wrote:
> On Wed, Jun 06, 2018 at 02:50:10PM +0100, Daniel P. Berrangé wrote:
> > On Wed, Jun 06, 2018 at 03:45:10PM +0200, Michal Suchánek wrote:
> > > 
> > > I think that *if* we want an 'appliance' format that stores a whole VM
> > > in a single file to ease VM distribution then the logical place to look
> > > in qemu is qcow. The reason have been explained at length.
> > 
> > I rather disagree. This is a common problem beyond just QEMU and everyone
> > just uses an existing archive format (TAR, ZIP) for bundling together
> > one or more disk images, metdata for config, and whatever other resources
> > are applicable for the vendor.  This works with any disk format (raw,
> > qcow2, vmdk, vpc, etc) so is preferrable to inventing someting that is
> > specific to qcow2 IMHO.
> 
> Now we have N+1 appliance file formats.  :)
> 
> (We like it or not, qcow2 is already used as an appliance format
> for single-disk VMs in practice.)
> 
> But I agree this must not be specific to qcow2.  The same VM
> description format we agree upon should work with other disk
> formats or with multi-disk appliances.
> 
> If we specify a reasonable VM description format for appliances
> and make it work inside (e.g.) tar files, we will still have the
> option of allowing the description be placed inside qcow2 if we
> really want to.  I don't think we need to finish this qcow2
> bikeshedding exercise right now.

Yes, I think that is sensible, as once we actually try it out in real
world cases, we might then find a tar/zip is sufficient after all and
we don't need to do something extra for qcow2. Also means we can do
experiments without committing to a qcow2 format spec change right
away.

Regards,
Daniel
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