Target Reset and Logical Unit Reset

Robert Snively rsnively at Brocade.COM
Mon Sep 17 10:42:45 PDT 2001


* From the T10 Reflector (t10 at t10.org), posted by:
* Robert Snively <rsnively at brocade.com>
*
Folks,

For further clarifications on the behavior of FCP-2, see 
paragraph 4.8, that indicates that all task management
functions invoked by the FCP_CMND IU are indicated as
complete by the FCP_RSP RSP_CODE of Task Management 
Function Complete.  A ladder diagram showing an example
of such behavior is in Annex B, paragraph B.1.9.
Many exchange clearing actions (Recovery Abort) may
be executed between the time the FCP_CMND IU is emitted
and the FCP_RSP is returned.

In general, FCP_RSP should be returned for all cases.
The use of a Recovery Abort applied to a task management
exchange is not disallowed, but should be used sparingly
if necessary to complete the cases TARGET RESET task 
management functions overlapping with other reset 
task management functions.  

For LOGICAL UNIT RESET functions that are overlapped,
the operations depend on the definition of task set for
the particular logical unit.  The definition of task set
is specified by the TST field in the control mode page, 
specified in 8.3.6 of SPC-2.  This does not apply to
TARGET RESET, which resets all tasks in all task sets.

Hope this adds more information, if not necessarily
clarification.

Bob Snively                        e-mail:    rsnively at brocade.com
Brocade Communications Systems     phone:  408 487 8135
1745 Technology Drive
San Jose, CA 95110


> -----Original Message-----
> From: Elliott, Robert [mailto:Robert.Elliott at COMPAQ.com]
> Sent: Monday, September 17, 2001 9:10 AM
> To: 't10 at t10.org'
> Subject: RE: Target Reset and Logical Unit Reset
> 

....

> In FCP-2, Table 5 says that the exchange is aborted for LOGICAL
> UNIT RESET, TARGET RESET, CLEAR TASK SET, and ABORT TASK SET.
> That serves as Function Complete for those functions.
>  
> Table 28 has a RSP_CODE value of 00h for "Task Management
> Function Complete" that's used only for CLEAR ACA.  The descriptive
> text is a bit confusing given table 5, but I think it makes sense
> if you assume it only applies to CLEAR ACA:
>   "The completion status of the task management function is
>   indicated by the RSP_CODE. If the Exchange is aborted before 
>   the FCP_RSP IU is returned, the completion status is unknown."
> 
> ABORT TASK is implemented using "recovery abort" per 12.3.
> 

...

> -----Original Message-----
> From: Nutter, John [mailto:jnutter at cereva.com]
> Sent: Monday, September 17, 2001 10:17 AM
> To: SCSI Reflector (E-mail)
> Subject: Target Reset and Logical Unit Reset
> 
> 
> I am trying to figure out what the expected behavior should 
> be under the
> following circumstances:
> Two different hosts send a Target Reset back to back.  Should 
> the target
> return a function complete to the first, last, or both Target Resets? 
> The same host sends a Target Reset back to back.  Should the 
> target return a
> function complete to the first, last, or both Target Resets? 
> A target receives a Logical Unit Reset and while processing 
> it the target
> receives a Target Reset from a different host.  Should the 
> target return a
> function complete to the Logical Unit Reset, the Target 
> Reset, or both? 
> A target receives a Logical Unit Reset and while processing 
> it the target
> receives a Target Reset from the same host.  Should the 
> target return a
> function complete to the Logical Unit Reset, the Target 
> Reset, or both? 
> Two different hosts send a Logical Unit Reset back to back to 
> the same LUN.
> Should the target return a function complete to the first, 
> last, or both
> Logical Unit Resets? 
> Two different hosts send a Logical Unit Reset back to back to 
> the same LUN.
> Should the target return a function complete to the first, 
> last, or both
> Logical Unit Resets? 
>  
> I would appreciate any responses.
>  
> Thanks
>  
> John J. Nutter              Phone:  (508) 787-5367
> Cereva Networks Inc.        Fax:    (508) 787-5002
> 3 Network Drive             e-mail: jnutter at cereva.com
> Marlborough, MA 01752-3083  web:    www.cereva.com
>  
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