Proposal for IEEE company_id based formats for FC-PH world-wideidentifiers

Mike Wenzel mw at
Wed Jan 8 17:41:43 PST 1997

* From the SCSI Reflector (scsi at, posted by:
* Mike Wenzel <mw at>
Hi Larry,

At 12:47 PM 1/8/97 PST, Larry Chen wrote:
>Hi Mike,
>I thought one of should send out email to record our recent conversation in
>this matter. I hope you don't mind if I use my notes.

Good idea.  The conclusions we came to are probably of interest to others
as well.

>Everyone agrees that the LUN WWN should be invariant (which happens to make
>the company_id + vendor specified id fields invariant too). So actually, 
>using the company_id + vendor specified id fields for the RAID controller 
>WWN is NOT ambiguous at all (and may not provide any additional utility). 

Yes, this is VERY important and I'm glad we all keep coming back to the
same conclusion!

In my previous memo, I said I was worried about using the WWN of a 
controller as the base for the WWN for a LUN, when the controller is
a field-replaceable unit (FRU).  I should have clarified that this
assumes that the WWN of the controller stays with the controller FRU
as it is moved around.  If the WWN stays with the "slot" that the
replacement plugs into, then it is invariant wrt the LUN and should
pose no problems with ambiguity.

>If the RAID controller's FRU WWN is needed, then there were two suggested
>1) Use the Device ID page - add FRU associations

Rod DeKoning made a proposal some time back where each item in the list
on the Device ID page would have an "association" field that could name
the entity being identified by that item.  This field does not appear in
either of Bob's tutorials or the most current SPC document.  I'm not sure
what became of the proposal, but it would have to be re-discussed to 
pursue this alternative.

>2) Use the ASCII Information page - on further observation, this page does 
>not provide the WWN of the FRU (but does have a Vendor-specific information
>field which could be used for this purpose).

It would be great if we could use standard mechanisms to locate all the
FRUs in a path to a chunk of storage.  Vendor-dependent mechanisms should
be a last resort.  I'd like to see this discussed by the Serial Solutions
group.  It's probably time to put together another agenda...

>Bye for now.

Best Regards,


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