Preservation of Sense Data

Tony DeLaCruz tdelacru at QNTM.COM
Mon Sep 22 11:25:25 PDT 1997


* From the T10 (formerly SCSI) Reflector (t10 at symbios.com), posted by:
* tdelacru at qntm.com (Tony DeLaCruz)
*
To all:

Question 1:
Is an I_T_L created for a LUN other than 0 when the Host uses a LUN greater than
0 (LUN defined via identify message) and the Target does not support multiple
LUNs?


Question 2:
I/O sequence for a target that does not support multiple LUNs:
1. Host issues a read for LUN 0 (LUN defined via identify message) that
generates a Check Condition (unrecoverable ECC error 0311h)
2. Host issues a Request Sense for LUN 1 (LUN defined via identify message),
target should return Sense Data 0525h (Illegal Request - Logical Unit Not
Supported) per section 7.5.3 case 'a' of the SCSI II specification.
3. Host issues a Request Sense for LUN 0 (LUN defined via identify message),
should target return Sense Data 0000h?

Should sense data from step 1 be wiped out or preserved? (I believe it should be
wiped out)

Section 7.6 of the SCSI II specification states: "The contingent allegiance
condition shall be preserved for the I_T_x nexus until it is cleared.  The
contingent allegiance condition shall be cleared upon the generation of a hard
reset condition, or by an ABORT message, a BUS DEVICE RESET message, or any
subsequent command for the I_T_x nexus.". 

The sense data from step 1 should be wiped out if the I_T_x nexus is the same
and preserved if the I_T_x nexus is the NOT same for step 1 - 3. Is this a true
statement? Is the I_T_x nexus the same for step 1 - 3 due to the fact that the
target device does not support multiple LUNs? 

Any help to better understand the preservation of Sense Data for targets that do
not support multiple LUNs would be greatly appreciated?


----------------------------------------------------------------

Tony De La Cruz

Quantum Corporation
500 McCarthy Blvd.
Milpitas, CA 95035
e-mail: tdelacru at qntm.com


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