SSC-3: Resolution to LB HPQ-70

Kevin D Butt kdbutt at us.ibm.com
Mon Sep 29 10:07:51 PDT 2008


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Aaah!  You are asking the question I was trying to highlight in my editors 
note.  By adding "on the BOP side" I have changed the behavior in the case 
you are asking about.  Prior to my change, if the PEWZ were small enough 
that a single write crossed into PEWZ and out into EW, then there would be 
no PEW CC but only the EW CC.  My proposed change would change this to 
require both CC's.  I think this is what was intended when I originally 
made the proposal to add PEWZ.	However, there was quite the discussion in 
the working group, especially by the ISV present, and I don't want to take 
anything for granted.
Given this change and looking at it again, I think I have under-specified 
the behavior.  I need to add that the PROGRAMMABLE EARLY
WARNING DETECTED CHECK CONDITION shall occur before the EW CC.
I am positive this will illicit a debate in the next SSC-3 WG meeting. 
This is why I asked for careful scrutiny.
Thanks,
Kevin D. Butt
SCSI & Fibre Channel Architect, Tape Firmware
MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
Tel: 520-799-2869 / 520-799-5280
Fax: 520-799-2723 (T/L:321)
Email address: kdbutt at us.ibm.com
http://www-03.ibm.com/servers/storage/ 
From:
"Knight, Frederick" <Frederick.Knight at netapp.com>
To:
Kevin D Butt/Tucson/IBM at IBMUS
Date:
09/29/2008 10:00 AM
Subject:
RE: SSC-3: Resolution to LB HPQ-70
I guess I wasn't clear.  For this case of transitioning out of PEWZ:
If you transition into PEWZ, and then transition out of PEWZ into EW, what 
do you get?
For example, the host mistakenly configures a PEWZ that is too small (so a 
large write
crosses into both zones).  Do you get:
BOTH check conditions (queued), or just the EW check condition (the PEWZ 
one is replaced)?
I assume based on the text I quoted, you get just the EW check condition; 
it is reported "instead".
    Fred
From: Kevin D Butt [mailto:kdbutt at us.ibm.com] 
Sent: Monday, September 29, 2008 12:44 PM
To: Knight, Frederick
Subject: RE: SSC-3: Resolution to LB HPQ-70
Fred, 
The Programmable Early Warning sets up an additional check condition prior 
to the Early Warning (EW) Check Condition.  So, IF an application client 
sets up PEWS in the mode page, then when the tape position crosses into 
PEWZ (i.e., location of EW - PEWS) then the new check condition is 
returned.  Then, presumably at a later time, when the tape position 
crosses into EW, the existing EW check condition will be returned.  So, 
the is a new CC prior to EW that is returned if and only if the mode page 
is set up to have this programmable early warning zone and there is the 
normal check condition(s) for EW.  As I recall, the application client 
will get a CC on every write after EW, but this might be configurable.	I 
can't find where you would configure it, but I know that some devices will 
report CC on each and every write after EW. 
Thanks, 
Kevin D. Butt
SCSI & Fibre Channel Architect, Tape Firmware
MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
Tel: 520-799-2869 / 520-799-5280
Fax: 520-799-2723 (T/L:321)
Email address: kdbutt at us.ibm.com
http://www-03.ibm.com/servers/storage/ 
From: 
"Knight, Frederick" <Frederick.Knight at netapp.com> 
To: 
Kevin D Butt/Tucson/IBM at IBMUS 
Date: 
09/29/2008 05:27 AM 
Subject: 
RE: SSC-3: Resolution to LB HPQ-70
Isn't there another CC that occurs when entering EW?  Am I remembering 
right (I didn't check)? 
Should there now be 2 CCs if you make it through PEWZ and into EW prior to 
the first PEWZ CC being delivered? or should the second one (entering EW) 
replace the PEWZ one?  It seems that you've covered this case by saying 
that if another condition occurs, then that condition shall be reported 
instead. 
If processing this command results in any 
other exception condition, the CHECK CONDITION status associated with that 
exception condition shall be 
reported instead. 
I have no issue with the changes you've proposed here. 
    Fred 
From: Kevin D Butt [mailto:kdbutt at us.ibm.com] 
Sent: Wednesday, September 24, 2008 5:02 PM
To: t10 at t10.org
Subject: SSC-3: Resolution to LB HPQ-70
I have posted a proposal (
http://www.t10.org/ftp/t10/document.08/08-389r0.pdf) to resolve SSC-3 
Letter Ballot comment LB HPQ-70 related to the programmable early warning 
indication that was added as part of the solicited ISV requests. 
Tim, Roger, and Ray, 
Please pay attention to the functional change this proposal makes.  It 
bears on when the CC will and will not be returned.  I thought the 
description was intended to be entering PEWZ and exiting on BOP side prior 
to the indication being given.	As written it also includes entering PEWZ 
and exiting into EW prior to CC being given.  I don't think that was our 
intent, but please check to make sure. 
Thanks, 
Kevin D. Butt
SCSI & Fibre Channel Architect, Tape Firmware
MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
Tel: 520-799-2869 / 520-799-5280
Fax: 520-799-2723 (T/L:321)
Email address: kdbutt at us.ibm.com
http://www-03.ibm.com/servers/storage/ 



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