[libvirt] [PATCH 09/13] qemu: support LUN numbers for iSCSI disks

Daniel P. Berrange berrange at redhat.com
Fri Mar 15 15:59:40 UTC 2013


On Fri, Mar 15, 2013 at 04:53:19PM +0100, Paolo Bonzini wrote:
> Il 15/03/2013 15:40, Daniel P. Berrange ha scritto:
> >> > Each iSCSI target can provide multiple logical units.  Support this
> >> > with an additional attribute in the <source> element.
> > Hmm, this is kind of what the 'name' attribute is used for with
> > RBD / Gluster. I tend to feel we should just use that rather
> > than adding a new attribute. eg
> > 
> >   <source name="<IQN>/<LUN>">
> 
> I think IQN and LUN are separate things, and best kept separate.  For
> example, for each IQN you can only have (if you use -readconfig, which
> this series doesn't do) a single username/password/initiator-name triple.
> 
> Note that the 'name' attribute is already used for the IQN.

Yes, but that doesn't make it right. The 'name' attribute is intended to
uniquely identify the exported volume on the server. Neither IQN or LUN
alone can uniquely identify the volume, so the "name" attribute should
use a combination of the two. This is the same scenario you have with
RBD, where you have a 'pool' and 'volume', so the "name" attribute
uses the "<pool>/<volume>" syntax for identifying the export. In
retrospect this combined syntax may have been better split up into
separate attributes, but that's what we have, so we should follow this
existing practice for iSCSI too.

Daniel
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