REPORT LUNS clarification suggestion

Elliott, Robert (Server Storage) elliott at hp.com
Wed Apr 21 09:22:41 PDT 2004


* From the T10 Reflector (t10 at t10.org), posted by:
* "Elliott, Robert (Server Storage)" <elliott at hp.com>
*
03-386 is Charles Binford's proposal to clean up REPORT LUNS when LUN 0
has a Peripheral Qualifier of 001b.

I think this basic approach might simplify matters:
REPORT LUNS returns the list of LUNs that will not generate CHECK
CONDITION/ILLEGAL REQUEST/LOGICAL UNIT NOT SUPPORTED to at least one
command other than REQUEST SENSE and INQUIRY. 

There are some inconsistent rules in SAM-3 and SPC-3 that need to be
corrected anyway. SAM-3 5.9.4 incorrect logical unit selection requires
terminating any command except REQUEST SENSE and INQUIRY if the
peripheral device "is not currently attached" (which presumably means
any LU with a PQ of 001b) with CC/IR/LU NOT SUPPORTED.  REPORT LUNS, by
not being excluded, must be subject to that rule.

This contradicts these other rules in SAM-3 and SPC-3: 
a) SAM-3: All SCSI devices shall accept LUN 0 as a valid address. 

b) SAM-3: Each SCSI target port shall accept commands sent to LUN 0 and
the task router shall route them to a device server for processing. The
REPORT LUNS commands (see SPC-3) shall be accepted by the logical unit
with the logical unit number zero from any SCSI target port and shall
return the logical unit inventory available via that SCSI target port. 

c) SPC-3: A SCSI device shall support a REPORT LUNS command that is
addressed to logical unit zero 


I think this rule set would self-consistent and clean that up: 
1) LUN 0 with PQ=001b only supports REPORT LUNS, REQUEST SENSE, and
INQUIRY, returning CC/IR/LU NOT SUPPORTED for other commands 

2) Other LUNs with PQ=001b only support REQUEST SENSE and INQUIRY,
returning CC/IR/LU NOT SUPPORTED for other commands 

3) LUN 0 is required to support REPORT LUNS command regardless of its
PQ. Other LUNS are not allowed to support that command while PQ=001b. 

4) REPORT LUNS returns LUN 0 plus LUNs that don't generate CC/IR/LU NOT
SUPPORTED for commands other than REQUEST SENSE and INQUIRY.
Essentially, it returns each LUN that supports at least one command
beyond INQUIRY and REQUEST SENSE. 



--
Rob Elliott, elliott at hp.com
Hewlett-Packard Industry Standard Server Storage Advanced Technology
https://ecardfile.com/id/RobElliott



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