SAM-2 status precedence - RESERVATION CONFLICT vs. CHECK CONDITON/UNIT ATTENTION/POWER ON OCCURRED

Elliott, Robert Robert.Elliott at COMPAQ.com
Mon Mar 25 15:37:44 PST 2002


* From the T10 Reflector (t10 at t10.org), posted by:
* "Elliott, Robert" <Robert.Elliott at COMPAQ.com>
*
That's the escape I hinted at with:
  Depending on how you interpret "more than one condition applies"
  this violates the SAM-2 precedence rule.

Does the reservation conflict condition exist immediately after power on, or only after the device server has decided it's finished reporting the power on and is ready to process a command?

If the logical unit is still loading its persistent reservation state and the command is one that could generate a reservation conflict, SPC-3 requires it return CHECK CONDITION/NOT READY.  This implies there may be some time before the reservation conflict must be known to exist, which might be enough to allow CHECK CONDITION/UNIT ATTENTION/POWER ON OCCURRED.  

On a logical unit that doesn't need that time, however, the SAM-2 rule can be interpreted as requiring or at least allowing that RESERVATION CONFLICT be returned immediately (no time for a CHECK CONDITION).  

Do we want all these sequences to be legal, or just some of them:
1) RESERVATION CONFLICT
...
n) CHECK CONDITION/UNIT ATTENTION/POWER ON OCCURRED;


1) CHECK CONDITION/UNIT ATTENTION/POWER ON OCCURRED; and
2) RESERVATION CONFLICT


1) CHECK CONDITION/UNIT ATTENTION/POWER ON OCCURRED;
2) CHECK CONDITION/NOT READY/LOGICAL UNIT IS IN PROCESS OF BECOMING READY; and
3) RESERVATION CONFLICT


1) CHECK CONDITION/NOT READY/LOGICAL UNIT IS IN PROCESS OF BECOMING READY; and
2) RESERVATION CONFLICT
...
n) CHECK CONDITION/UNIT ATTENTION/POWER ON OCCURRED;


1) CHECK CONDITION/NOT READY/LOGICAL UNIT IS IN PROCESS OF BECOMING READY;
2) CHECK CONDITION/UNIT ATTENTION/POWER ON OCCURRED; and
3) RESERVATION CONFLICT

---
Rob Elliott, Compaq? Server Storage
Robert.Elliott at compaq.com


> -----Original Message-----
> From: Peter Johansson [mailto:PJohansson at acm.org]
> Sent: Monday, March 25, 2002 4:56 PM
> To: NCITS T10
> Subject: Re: SAM-2 status precedence - RESERVATION CONFLICT vs.
> CHECKCONDITON/UNIT ATTENTION/POWER ON OCCURRED
> 
> 
> * From the T10 Reflector (t10 at t10.org), posted by:
> * Peter Johansson <PJohansson at ACM.org>
> *
> At 01:42 PM 3/25/2002 -0600, Elliott, Robert wrote:
> 
> >5.3.2 Status precedence
> >If more than one condition applies to a completed task, the 
> report of a 
> >BUSY, RESERVATION CONFLICT, ACA ACTIVE or TASK SET FULL 
> status shall take 
> >precedence over the return of any other status for that task.
> 
> Maybe I'm reading this in an idiosyncratic fashion, but it 
> seems to me 
> there is no problem. I read the text above as how to select 
> one condition 
> amongst possibly many SIMULTANEOUSLY CREATED conditions. In 
> other words, 
> there is no conflict between the UNIT ATTENTION CHECK 
> CONDITION because the 
> device server doesn't event get to the point where it realizes a 
> RESERVATION CONFLICT exists.
> 
> I may be overlooking some fundamental aspect of SAM, but I suspect my 
> confusion may be instructive for the debate.
> 
> 
> Regards,
> 
> Peter Johansson
> 
> Congruent Software, Inc.
> 98 Colorado Avenue
> Berkeley, CA  94707
> 
> (510) 527-3926
> (510) 527-3856 FAX
> 
> PJohansson at ACM.org
> 
> *
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