Interpretation of Logical unit Reset behavior

gerry.houlder at seagate.com gerry.houlder at seagate.com
Fri Oct 18 14:25:58 PDT 2002


* From the T10 Reflector (t10 at t10.org), posted by:
* gerry.houlder at seagate.com
*
A contradiction has been pointed out for the description of the Logical
Unit Reset behavior. In particular, note the requirements I have marked
with double brackets << >>.

>From SPI - 4 or 5:

   16.5.6 LOGICAL UNIT RESET
   The LOGICAL UNIT RESET message is defined in the SCSI Architecture
   Model-2 standard.
   Receipt of the LOGICAL UNIT RESET message after an I_T_L nexus has been
   established is a logical
   unit reset event as defined in the SCSI Architecture Model-2 standard.
   In addition to the requirements in the SCSI Architecture Model-2
   standard the SCSI target port shall go to
   the BUS FREE phase following the successful receipt of the LOGICAL UNIT
   RESET message.

   <<A logical unit reset has no effect on the transfer agreement.>>

>From SCSI Architecture Model-2 standard

   5.9.7 Logical unit reset
   A logical unit reset is:
   a) The action in response to a LOGICAL UNIT RESET task management
   request (see 6.6) or some other
   logical unit reset event; or
   b) One of the actions in response to a TARGET RESET task management
   function (see 6.7) or a hard reset
   (see 5.9.6).
   The definition of logical unit reset events is dependent on the SCSI
   transport protocol.
   To process a logical unit reset the logical unit shall:
   a) Abort all tasks as described in 5.7;
   b) Clear a CA (see 5.9.1.6) or ACA (see 5.9.1.7) condition, if one is
   present;
   c) Release all reservations established using the reserve/release
   management method (persistent reserva-tions
   shall not be affected);
   <<d) Return the logical unit's operating mode to the appropriate initial
   conditions, similar to those conditions that
   would be found following device power-on.>> The MODE SELECT parameters
   (see SPC-2) shall be restored
   to their last saved values if saved values have been established. MODE
   SELECT parameters for which no
   saved values have been established shall be returned to their default
   values;
   e) Set an unit attention condition (see 5.9.5); and
   f) Initiate a logical unit reset for all dependent logical units (see
   4.13).
   In addition to the above, the logical unit shall perform any additional
   functions required by the applicable standards.

The wording from SPI says "no effect on transfer agreement", meaning the
target has to remember the transfer agreement even though everything else
is being reset. The SAM wording says "similar to power on", which certainly
includes resetting the transfer agreement. These conditions certainly
conflict with each other. How do we resolve the conflicting wording?

The single LUN targets I am familiar with reset all the same things
(including the transfer agreement) for both of these functions. Are these
devices in violation of the standard?

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