Task Management

Larry Chen larryc at maxstrat.com
Tue May 12 16:13:33 PDT 1998


* From the T10 (formerly SCSI) Reflector (t10 at symbios.com), posted by:
* Larry Chen <larryc at maxstrat.com>
*
     
On Tue, 12 May 1998 09:24:58 -0700 (PDT)  Bob Snively wrote:
>* From the T10 (formerly SCSI) Reflector (t10 at symbios.com), posted by:
>* Bob Snively <Bob.Snively at Eng.Sun.COM>
>*
>
>Folks,
>
>A properly implemented software convention using the persistent reserve
>function appears to me to be precisely what Larry is looking for.
>
>Bob
Hi Bob,

I am trying to implement a simple and highly reliable command timeout
error recovery scheme at the SIM layer. 

My philosophy is to use the BIGGEST hammer allowable for a
multi-initiator FC-AL environment which will prevent ping-pong
actions between the initiators.

In the good old days of parallel SCSI, SCSI Bus Reset could be sent.
If my memory serves me correctly, SCSI Bus Resets were seen by all
devices (including other initiators). The important point being that
ULP timeouts were NOT relied upon to retry the command(s) that were
aborted due to SCSI Bus Reset.

For FC-AL, SCSI Bus Reset is NOT available and can NOT be properly
emulated, especially for multi-initiator environments.
IMHO, anything less than SCSI Bus Reset is unreliable. Therefore,
I envision at least two hammers will be needed now.

1) one based on Abort Task Set or LIP without issuing ADISC/PDISC
Note - with Lun spaces growing to 8 bytes, I think the SIM will
be hard pressed to send Abort Task Set to all luns (including
multi-lun devices).
2) one based on Target Reset

-Larry

>
>> * From the T10 (formerly SCSI) Reflector (t10 at symbios.com), posted by:
>> * ROWEBER at acm.org
>> *
>> Larry,
>> 
>> > I would like to issue a single Task Management Request (TMR) to Lun 0, 
>> > which will abort all commands under the target device belonging to the
>> > requesting initiator.  (i.e., Abort Task Set is issued to all valid lun
>> > devices under the target device).
>> >
>> > Logical Unit Reset is a little too harsh for multi-initiator environments.
>> 
>> Sorry, no such task management function exists currently.  One could
>> propose addition of the function in any of several ways that would
>> result in changes to one or more of SAM-2, SPC-2, SPI-3, and FCP-2.
>> 
>> Ralph...
>> *
>> * For T10 Reflector information, send a message with
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>
>*
>* For T10 Reflector information, send a message with
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-------------------------------------------------------
Larry Chen             Tel: 408.383.1600 (x116)
MAXSTRAT Corporation   Fax: 408.383.1616
801 Buckeye Court      E-mail: larryc at maxstrat.com
Milpitas, CA 95035     URL: http://www.maxstrat.com/
-------------------------------------------------------



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