SSC-4: Programmable Early Warning question

Dennis Painter dennis at hale-pohaku.net
Fri Oct 2 14:08:31 PDT 2009


* From the T10 Reflector (t10 at t10.org), posted by:
* Dennis Painter <dennis at hale-pohaku.net>
*
Hi Kevin,
I think (b) is a the best way to cover this.It should  not disrupt any
application software.
It would think it will also cover use of the SET CAPACITY command.
Thanks,
Dennis
Kevin D Butt wrote:
>
> Dennis,
>
> The RECOVERED ERROR/PARAMETERS ROUNDED response is specified in SPC-4
> for use when parameters are rounded.	This should be what we do at a
> minimum.
> There is no restriction on a volume being loaded and I suspect that
> the users of the PEWS would not want there to be this restriction.
>  This drives an implementer to either chose:
> a)  a maximum supported value that is less than the native capacity of
> the volumes supported (though Set Capacity could mess that up); or
> b) on volume state changing from unmounted to mounted, checking PEWS
> field and, if necessary, modify the value to the now current maximum
> value and establish a UA for MODE PARAMETERS CHANGED.
>
> I am not sure that either solution is ideal, but I think either
> solution would work - or a combination of both where the UA would only
> be required if the capacity of a supported volume had been modified by
> a Set Capacity command to a capacity less than the value chosen for
> the maximum PEWS value supported.  I suspect that users would really
> only desire a max capacity of somewhere less than about 10 GB.
>  However, I don't think we should limit ourselves to that in the
> standard.
>
> Thanks,
>
> Kevin D. Butt
> SCSI & Fibre Channel Architect, Tape Firmware
> 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: 	Dennis Painter <dennis at hale-pohaku.net>
> To:	"t10 at t10.org" <t10 at t10.org>
> Date: 	10/02/2009 09:46 AM
> Subject:	Re: SSC-4: Programmable Early Warning question
>
>
> ------------------------------------------------------------------------
>
>
>
> * From the T10 Reflector (t10 at t10.org), posted by:
> * Dennis Painter <dennis at hale-pohaku.net>
> *
> Protection from it being set to a value greater that the media capacity
> is good. I favor recovered error as the software can accept it and
> continue or has the option to read the PEWS setting.
>
> Is it allowed for the application client to set PEWS if there is no
> media present? I did not find a restriction in the current draft but it
> may not be where I looked.
>
> If not restricted and media of different capacity is supported then
> there is a potential problem of PEWS being set for a larger capacity
> tape and having a smaller capacity tape inserted. If PEWS is cleared on
> media removal and cannot be set without media present then there would
> be no issue.
>
> Dennis Painter
>
>
> Ballard, Curtis C (StorageWorks) wrote:
> > In the interest of having a complete specification it would be
> > appropriate to specify behavior although I would hope that an
> > application would never make that mistake.
> >
> > Rather than reject the command I would be inclined to have a device
> > specific maximum PEWS zone and report a recovered error with the PEWS
> > zone set to the maximum allowed.
> >
> > Curtis Ballard
> > Hewlett Packard
> >
> > ------------------------------------------------------------------------
> > *From:* owner-t10 at t10.org [mailto:owner-t10 at t10.org] *On Behalf Of
> > *Kevin D Butt
> > *Sent:* Thursday, October 01, 2009 1:46 PM
> > *To:* t10 at t10.org
> > *Subject:* SSC-4: Programmable Early Warning question
> >
> >
> > Tapeheads,
> >
> > I wonder if we should protect the programmable early warning from
> > being set to too large a value.  Should we add some statement like the
> > following to SSC-4?
> >
> > If PEWS field of Device Configuration Extension mode page is set to a
> > value larger than the tapes capacity, then the Mode Select should be
> > rejected with ILLEGAL REQUEST, INVALID FIELD IN PARAMETER LIST.
> >
> > Thanks,
> >
> > Kevin D. Butt
> > SCSI & Fibre Channel Architect, Tape Firmware
> > 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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> Content-Transfer-Encoding: 7bit
>
> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
> Protection from it being set to a value greater that the media
> capacity is good. I favor recovered error as the software can accept
> it and continue or has the option to read the PEWS setting.
>
> Is it allowed for the application client to set PEWS if there is no
> media present? I did not find a restriction in the current draft but
> it may not be where I looked.
>
> If not restricted and media of different capacity is supported then
> there is a potential problem of PEWS being set for a larger capacity
> tape and having a smaller capacity tape inserted. If PEWS is cleared
> on media removal and cannot be set without media present then there
> would be no issue.
>
> Dennis Painter
>
>
> Ballard, Curtis C (StorageWorks) wrote:
> >In the interest of having a complete specification it would be
> appropriate to specify behavior although I would hope that an
> application would never make that mistake.
> >
> >Rather than reject the command I would be inclined to have a device
> specific maximum PEWS zone and report a recovered error with the PEWS
> zone set to the maximum allowed.
> >
> >Curtis Ballard
> >Hewlett Packard
> >
> >
> >----------
> >From: <mailto:owner-t10 at t10.org>owner-t10 at t10.org
> [mailto:owner-t10 at t10.org] On Behalf Of Kevin D Butt
> >Sent: Thursday, October 01, 2009 1:46 PM
> >To: <mailto:t10 at t10.org>t10 at t10.org
> >Subject: SSC-4: Programmable Early Warning question
> >
> >
> >Tapeheads,
> >
> >I wonder if we should protect the programmable early warning from
> being set to too large a value.  Should we add some statement like the
> following to SSC-4?
> >
> >If PEWS field of Device Configuration Extension mode page is set to a
> value larger than the tapes capacity, then the Mode Select should be
> rejected with ILLEGAL REQUEST, INVALID FIELD IN PARAMETER LIST.
> >
> >Thanks,
> >
> >Kevin D. Butt
> >SCSI & Fibre Channel Architect, Tape Firmware
> >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/
>
> --------------050506040709020403060503--
>
> *
> * For T10 Reflector information, send a message with
> * 'info t10' (no quotes) in the message body to majordomo at t10.org
>
>
--------------010906030203020303000607
Content-Type: text/html; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
Hi Kevin,
I think (b) is a the best way to cover this.It should  not disrupt any
application software. 
It would think it will also cover use of the SET CAPACITY command.
Thanks,
Dennis
Kevin D Butt wrote: 
>Dennis, 
>
>The RECOVERED ERROR/PARAMETERS ROUNDED response is specified in SPC-4 for
use when parameters are rounded.  This should be what we do at a minimum.   
>There is no restriction on a volume being loaded and I suspect that the
users of the PEWS would not want there to be this restriction.	This drives
an implementer to either chose: 
>a)  a maximum supported value that is less than the native capacity of the
volumes supported (though Set Capacity could mess that up); or 
>b) on volume state changing from unmounted to mounted, checking PEWS field
and, if necessary, modify the value to the now current maximum value and
establish a UA for MODE PARAMETERS CHANGED. 
>
>I am not sure that either solution is ideal, but I think either solution
would work - or a combination of both where the UA would only be required if
the capacity of a supported volume had been modified by a Set Capacity
command to a capacity less than the value chosen for the maximum PEWS value
supported.  I suspect that users would really only desire a max capacity of
somewhere less than about 10 GB.  However, I don't think we should limit
ourselves to that in the standard. 
>
>Thanks, 
>
>Kevin D. Butt
>SCSI & Fibre Channel Architect, Tape Firmware
>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: Dennis Painter <mailto:dennis at hale-pohaku.net><dennis at hale-pohaku.net> >To: <mailto:t10 at t10.org>"t10 at t10.org" <mailto:t10 at t10.org><t10 at t10.org> 
>Date: 10/02/2009 09:46 AM 
>Subject: Re: SSC-4: Programmable Early Warning question 
>
>
>
>
>
>* From the T10 Reflector (<mailto:t10 at t10.org>t10 at t10.org), posted by:
>* Dennis Painter <mailto:dennis at hale-pohaku.net><dennis at hale-pohaku.net>
>*
>Protection from it being set to a value greater that the media capacity 
>is good. I favor recovered error as the software can accept it and 
>continue or has the option to read the PEWS setting.
>
>Is it allowed for the application client to set PEWS if there is no 
>media present? I did not find a restriction in the current draft but it 
>may not be where I looked.
>
>If not restricted and media of different capacity is supported then 
>there is a potential problem of PEWS being set for a larger capacity 
>tape and having a smaller capacity tape inserted. If PEWS is cleared on 
>media removal and cannot be set without media present then there would 
>be no issue.
>
>Dennis Painter
>
>
>Ballard, Curtis C (StorageWorks) wrote:
>> In the interest of having a complete specification it would be 
>> appropriate to specify behavior although I would hope that an 
>> application would never make that mistake.
>>  
>> Rather than reject the command I would be inclined to have a device 
>> specific maximum PEWS zone and report a recovered error with the PEWS 
>> zone set to the maximum allowed.
>>  
>> Curtis Ballard
>> Hewlett Packard
>>
>> ------------------------------------------------------------------------
>> *From:* <mailto:owner-t10 at t10.org>owner-t10 at t10.org
[mailto:owner-t10 at t10.org] *On Behalf Of 
>> *Kevin D Butt
>> *Sent:* Thursday, October 01, 2009 1:46 PM
>> *To:* <mailto:t10 at t10.org>t10 at t10.org
>> *Subject:* SSC-4: Programmable Early Warning question
>>
>>
>> Tapeheads,
>>
>> I wonder if we should protect the programmable early warning from 
>> being set to too large a value.  Should we add some statement like the 
>> following to SSC-4?
>>
>> If PEWS field of Device Configuration Extension mode page is set to a 
>> value larger than the tapes capacity, then the Mode Select should be 
>> rejected with ILLEGAL REQUEST, INVALID FIELD IN PARAMETER LIST.
>>
>> Thanks,
>>
>> Kevin D. Butt
>> SCSI & Fibre Channel Architect, Tape Firmware
>> 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/ 
>
>--------------050506040709020403060503
>Content-Type: text/html; charset=ISO-8859-1
>Content-Transfer-Encoding: 7bit
>
><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
>Protection from it being set to a value greater that the media capacity is
good. I favor recovered error as the software can accept it and continue or
has the option to read the PEWS setting.
>
>Is it allowed for the application client to set PEWS if there is no media
present? I did not find a restriction in the current draft but it may not be
where I looked.
>
>If not restricted and media of different capacity is supported then there is
a potential problem of PEWS being set for a larger capacity tape and having a
smaller capacity tape inserted. If PEWS is cleared on media removal and
cannot be set without media present then there would be no issue.
>
>Dennis Painter
>
>
>Ballard, Curtis C (StorageWorks) wrote: 
>>In the interest of having a complete specification it would be appropriate
to specify behavior although I would hope that an application would never
make that mistake.
>> 
>>Rather than reject the command I would be inclined to have a device
specific maximum PEWS zone and report a recovered error with the PEWS zone
set to the maximum allowed.
>> 
>>Curtis Ballard
>>Hewlett Packard
>>
>>
>>----------
>>From:
<<mailto:owner-t10 at t10.org>mailto:owner-t10 at t10.org><mailto:owner-t10 at t10.org
>owner-t10 at t10.org [<mailto:owner-t10 at t10.org>mailto:owner-t10 at t10.org] On
Behalf Of Kevin D Butt
>>Sent: Thursday, October 01, 2009 1:46 PM
>>To: <<mailto:t10 at t10.org>mailto:t10 at t10.org><mailto:t10 at t10.org>t10 at t10.org
>>Subject: SSC-4: Programmable Early Warning question
>>
>>
>>Tapeheads, 
>>
>>I wonder if we should protect the programmable early warning from being set
to too large a value.  Should we add some statement like the following to
SSC-4? 
>>
>>If PEWS field of Device Configuration Extension mode page is set to a value
larger than the tapes capacity, then the Mode Select should be rejected with
ILLEGAL REQUEST, INVALID FIELD IN PARAMETER LIST. 
>>
>>Thanks, 
>>
>>Kevin D. Butt
>>SCSI & Fibre Channel Architect, Tape Firmware
>>MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
>>Tel: 520-799-5280
>>Fax: 520-799-2723 (T/L:321)
>>Email address:
<mailto:kdbutt at us.ibm.com><mailto:kdbutt at us.ibm.com
>kdbutt at us.ibm.com
>><http://www-03.ibm.com/servers/stora">http://www-03.ibm.com/servers/storage/>http://www-03.ibm.com/servers/stora
ge/ 
>
>--------------050506040709020403060503--
>
>*
>* For T10 Reflector information, send a message with
>* 'info t10' (no quotes) in the message body to
<mailto:majordomo at t10.org>majordomo at t10.org
>
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