[libvirt] [PATCH alt] conf: Allow user define their own alias

[Daniel P. Berrange]

On Fri, Sep 29, 2017 at 01:04:34PM +0200, Michal Privoznik wrote:
> On 09/29/2017 10:49 AM, Daniel P. Berrange wrote:
> > On Fri, Sep 29, 2017 at 09:06:01AM +0200, Michal Privoznik wrote:
> >> https://bugzilla.redhat.com/show_bug.cgi?id=1434451
> >>
> >> It comes handy for management application to be able to have a
> >> per-device label so that it can uniquely identify devices it
> >> cares about. The advantage of this approach is that we don't have
> >> to generate aliases at define time (non trivial amount of work
> >> and problems). The only thing we do is parse the user supplied
> >> tag and format it back. For instance:
> >>
> >>     <disk type='block' device='disk'>
> >>       <driver name='qemu' type='raw'/>
> >>       <source dev='/dev/HostVG/QEMUGuest1'/>
> >>       <target dev='hda' bus='ide'/>
> >>       <alias user='myDisk0'/>
> > 
> > I really do not like this - having two arbitrary string alias names is
> > just crazy. 
> 
> Why is that? We have plenty of elements that do not match to anything at
> hypervisor level. Firstly, there's metadata. Secondly, aliases in lxc
> driver don't match anything either. And one can argue that the link in
> qemu can be broken too. I mean, it's just for now that the aliases we
> report happen to be device IDs we put onto the qemu's cmd line. Not to
> mention devices that we put there and not report in the domain XML => no
> IDs visible there.

> > If we want to add a second attribute to uniquely identify
> > devices, then it should be a UUID IMHO, so it at least has some tangible
> > benefit instead of just duplicating the existing id format
> 
> I'm failing to see why UUID is better than any arbitrary string. You
> mean we would generate the UUIDs if not supplied by user?

Some hypervisors could map UUIDs to individual devices, so it is a more
generally useful concept.

Regards,
Daniel
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