[Libvir] Supporting new Xen 3.0.3 blktap backend for file devices

[Daniel Veillard]

On Wed, Sep 27, 2006 at 07:05:38PM +0200, Karel Zak wrote:
> On Tue, Sep 26, 2006 at 08:08:33PM +0100, Daniel P. Berrange wrote:
> > 
> > This means the easy option of just making all file devices use blktap in
> > 3.0.3 is not practical. This in turns means we need to  come up with a
> > way to express the new driver methods in libvirt XML. There are a few
> > options I can think of :
> > 
> >  - Allow more values in the 'type' attribute, eg file, block, blktap:aio,
> >    blktap:qcow, etc. This feels wrong because the blktap:* entries are
> >    really still 'file' types.
> > 
> >  - Introduce a new attribute  'driver'  where you can specify 'loop',
> >    'blktap:aio', 'blktap:qcow', etc
> > 
> >  - Introduce a new element 'driver' where you can specify the same
> > 
> >        <disk type="file">
> >           <driver type='blktap:aio'/>
> >        </disk>
> > 
> >  - Same as above, but normalize the driver type further
> > 
> >        <disk type="file">
> >          <driver type='blktap' backend='aio' />
> >        </disk>
> > 
> > My preference is probably option 3 or 4.
> 
>  My preference is definitely 4.
>  
>  (well, I'm affected by Database Normalization where it's bad merge
>  two information into one attribute -- so 'blktap:aio' is wrong way
>  ;-)

  I would agree that rather than glueing it's better to separate the 2 strings
as separate attributes. But should the second be named 'backend' or something
more generic like 'subtype'. That's the only slight concern I have but it's
probably better to be explicit about and the suggested form is just fine.
Let's go for 4/ :-)

Daniel

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