SAM-5 definition of physical reconfiguration

Kevin D Butt kdbutt at us.ibm.com
Wed Jan 7 06:58:16 PST 2015


Formatted message: <a href="http://www.t10.org/cgi-bin/ac.pl?t=r&f=r1501073_f.htm">HTML-formatted message</a>

To through in a specific example of the MODE SELECT scenario, in ADC the 
library can modify the WWPN of the Tape drives primary port. Therefore, 
ADC defines a way to change the port - this is like physically changing 
who the port is. To some, this meets the definition of physical 
reconfiguration because the old port went away and a new port came into 
existence.
Kevin D. Butt
SCSI Architect, Tape Firmware, T10 Standards
Data Protection & Retention
MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
Tel: 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:	"Ballard, Curtis C (HP Storage)" <curtis.ballard at hp.com>, 
"Ericson, George" <george.ericson at emc.com>, Gerry Houlder 
<gerry.houlder at seagate.com>, T10 Reflector <t10 at t10.org>
Date:	01/07/2015 07:31 AM
Subject:	RE: SAM-5 definition of physical reconfiguration
Sent by:	<owner-t10 at t10.org>
And to add to Georges point.
Yes, the INQUIRY DATA HAS CHANGED is a must (since the VPD page data would 
change); AND
An ASYMMETRIC ACCESS STATE CHANGED unit attention would also be 
appropriate, since the REPORT TARGET PORT GROUPS returned parameter data 
would also have changed.
Now, the question of course, about the ASYMMETRIC ACCESS STATE CHANGED 
unit attention ? is whether hosts assume that ONLY states changed (did the 
host interpret this UA literally?), or if they interpret that unit 
attention in the broader sense that ?stuff? in the REPORT TARGET PORT 
GROUPS response data has changed.
		Fred
From: Knight, Frederick 
Sent: Wednesday, January 07, 2015 9:13 AM
To: 'Ballard, Curtis C (HP Storage)'; Ericson, George; Gerry Houlder; T10 
Reflector
Subject: RE: SAM-5 definition of physical reconfiguration
I guess I tend to think of those words ?physical  reconfiguration? as 
meaning something happened that is ?outside the scope of the standard?.  I 
never considered whether it was S/W or H/W that cause the change just that 
something outside what was documented in the standards had happened.
If it was just a MODE SELECT command that cause the change, then I?d 
expect something in the standard to describe it.  Since there is nothing 
to describe it, then I?d tend to say that a MODE SELECT doesn?t change 
that kind of stuff.
		Fred
From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Ballard, 
Curtis C (HP Storage)
Sent: Tuesday, January 06, 2015 5:54 PM
To: Ericson, George; Gerry Houlder; T10 Reflector
Subject: RE: SAM-5 definition of physical reconfiguration
I?m not certain that just removing ?physical? solves the problem but I do 
agree that reconfiguration of virtual SCSI target devices can and should 
be able to cause this.	We have devices that are able to be software 
reconfigured so that virtual ports are enabled/disabled and we consider 
that to ?virtually? be a physical reconfiguration.
The last time I looked at this we concluded that it took something 
significant like a port add/delete to justify changing a relative port 
identifier and that an external change like a cable pull/plug or a SCSI 
change like an ADI port enable/disable command shouldn?t cause a change.
Curtis Ballard
Hewlett Packard
From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Ericson, 
George
Sent: Tuesday, January 6, 2015 3:37 PM
To: Gerry Houlder; T10 Reflector
Subject: RE: SAM-5 definition of physical reconfiguration
The simple fix is to remove the word ?physical? from the referenced 
sentence.   Reconfiguration of ?virtual? SCSI target devices has been the 
practice for a very long time.	I expect an INQUIRY DATA HAS CHANGED 
event.
George
From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Gerry 
Houlder
Sent: Tuesday, January 06, 2015 4:52 PM
To: T10 Reflector
Subject: Re: SAM-5 definition of physical reconfiguration
i tend to think of physical reconfiguration as a hardware change thing. 
Changing cables around, moving a card from one slot to another, flicking a 
switch. Things that are outside the scope of SCSI standards. i would 
consider things that can be done with SCSI commands (e.g., MODE SELECT) to 
be more of a logical reconfiguration that should't change a port 
identifier.
I will concede that we are now defining SCSI commands that can create or 
remove logical units. This allows commands to create a virtual logical 
unit in one location, tear it down, and recreate the same numbered logical 
unit in another location within the same domain and have the same result 
as swapping some cables or moving a PC card from one backpanel slot to 
another. This muddies things a bit.
On Tue, Jan 6, 2015 at 3:10 PM, Kevin D Butt <kdbutt at us.ibm.com> wrote:
In 4.6.5.2 of SAM-5r18 there is the following sentence. 
The relative port identifier for a SCSI port shall not change once 
assigned unless physical reconfiguration of the SCSI target device occurs. 
What is the definition of "physical reconfiguration"? 
Within my company I have opinions that oppose each other. 
 1) physically change cables that are connected 
 2) change the configuration settings (e.g., mode select) 
Thanks, 
Kevin D. Butt
SCSI Architect, Tape Firmware, T10 Standards
Data Protection & Retention
MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
Tel: 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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