Re: [PATCH] zfcp: Report FCP LUN to SCSI midlayer

[Doug Maxey <dwm@enoyolf.org>]

On Fri, 22 Jun 2007 09:11:39 CDT, James Bottomley wrote:
> On Thu, 2007-06-21 at 21:40 -0700, Mike Anderson wrote:
> > James Bottomley <James.Bottomley@SteelEye.com> wrote:
> > > A proposal to display the correct form of the LUN would be useful if you
> > > wish to make it? ...  The problem is really that SAM specifies a
> > > possible 4 level structure with 4 possible address methods per level.
> > > 
> > > The well known LUNs should be simple; there are only three: Report Lun,
> > > Access Controls and Target Log Pages.  The rest we really need input on.
> > > For instance, I could see the vendors wishing us to combine a
> > > multi-level flat addressing space into a single logical unit number,
> > > whereas I could see them wanting us to supply some sort of hierarchy for
> > > the peripheral and logical unit methods of addressing.
> > > 
> > > Since you're already using 2 level flat addressing, how do you want to
> > > see that represented?
> > 
> > James, why would we would not want to display the lun per SAM4 4.6.2 as
> > suggested by Stefan in a previous comment.
> 
> Because in a two LUN system, what was LUN 1 would then become LUN
> 0x1000000000000 which looks a bit unpalatable.
> 

Just my $.02.

If you use a pseries, and have to specifiy the LUN to the OFW on the later 
releases, you must train the fingers to type the extra 12 chars.  

Iy you are watching an iSCSI target with tcpdump, you can observe the 
PDU fields with the lun encoded thusly.   It may not be historical, but 
is certainly more accurate to use the 0x1000000000000 as 64 bit (or 
more correctly 8 bytes) encoded as hex.

++doug