[libvirt] Domain XML format using defined storage volume + RFC

[Daniel P. Berrange]

On Thu, May 15, 2008 at 03:37:14PM +0200, Stefan de Konink wrote:
> On Thu, 15 May 2008, Daniel P. Berrange wrote:
> 
> > On Thu, May 15, 2008 at 03:20:06PM +0200, Stefan de Konink wrote:
> > > On Thu, 15 May 2008, Stefan de Konink wrote:
> > >
> > > > Now I wonder, is it possible to have here
> > > > somethinglike storage://netapp/lun-0?
> > > >
> > >
> > > [snip]
> > >
> > > > From the standpoint: we make it easy for the user I would prefer not to
> > > > provide a Linux specific path.
> > >
> > > http://libvirt.org/formatdomain.html#elementsDisks
> > >
> > > I propose an extension to the current <source> tag specifying where a disk
> > > should come from. In my humble opinion something that is already available
> > > inside libvirt should be reused.
> > >
> > > Therefore:
> > >
> > > source
> > >     If the disk type is "file", then the file attribute specifies the
> > > fully-qualified path to the file holding the disk. If the disk type is
> > > "block", then the dev attribute specifies the path to the host device to
> > > serve as the disk.
> > >
> > >     If the disk type is "pool", then the pool attribute and the volume
> > > attibute specify what volume should be used for this disk.
> >
> > I'd support a syntax like this:
> >
> >     <disk type="pool">
> >       <source pool="myfiler" vol="lun-4"/>
> >       <target dev="xvda"/>
> >     </disk>
> 
> I understand your point :) Nevermind, I think you are right, making a CD
> that is backed by a LUN is non-sence anyway.

A storage pool is not just SCSI. It can be a directory of ISO files, an NFS
mount of ISO files, local device nodes (including CDROM). So it is perfectly
possible that we'll use a pool to back a virtual CD device. This is dealt
with by simply specifying the 'device='cdrom' attribute. This shouldn't impact
the implementation since the choice of backend storage is completely independant
of the type of disk device emulated in the guest. For a CD you'd just use:

      <disk type="pool" device="cdrom">
        <source pool="myfiler" vol="lun-4"/>
        <target dev="hdc"/>
      </disk>

Regards,
Daniel.
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