ADC-2: Logical Unit mode pages "ENABLE" bit

Rose, Roger Rrose at tandbergdata.com
Wed Sep 12 16:58:06 PDT 2007


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Kevin,
This has been reworded a bit from the old ADC, apparently to include
task management requests.  Perhaps the wording needs to be cleaned up a
bit.  What would the normal response be for a LUN that reports 001b for
its peripheral qualifier in the Inquiry data?
Some mention of the "DT device primary port(s)" needs to be maintained,
since you still need the LUNs responsive to the ADT port when the LUNs
are disabled .	Failure to respond on the ADT port could be extremely
frustrating to recover from, especially if the mode page was saved with
ENABLE=0.
-roger
________________________________
From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Kevin D
Butt
Sent: Wednesday, September 12, 2007 4:06 PM
To: t10 at t10.org
Subject: ADC-2: Logical Unit mode pages "ENABLE" bit
Clause 6.2.2.3.3 of ADC-2r8 has the following sentence. 
An ENABLE bit set to zero specifies that the DT device primary port(s)
associated with the SMC logical unit shall not respond to commands and
task management requests received on the DT device primary port(s) 
Clause 6.2.2.3.3 SMC logical unit descriptor format is describing
Logical units and how they are configured.  It seems to me that the
enable bit should be related to how the SMC logical unit behaves and not
how a port behaves.  In my thinking the enable bit should be enabling
the logical unit or disabling it.  The correct response to a command
directed at it should be to return a 5/2500 ILLEGAL REQUEST LOGICAL UNIT
NOT SUPPORTED.	As ADC-2 reads it says the port shall not respond to any
commands or task management functions received on the device primary
port(s).  So I cannot respond to anything directed at LUN 0 either. 
If you make a stretch and say that "the DT device primary port(s)
associated with the SMC logical unit" means that it only applies to the
port when the LUN field specifies the SMC logical unit, then we have the
behavior that the device drops all requests that are either commands or
task management requests and makes no response to the host.  This seems
weird to have a port respond to transport specific communications (e.g.,
selection, LIP, etc) and to requests targeted at other LUNs but to go
silent and not respond to those directed at a specific LUN.  I think the
HBA will think the device has disappeared or has hung. 
This is the same wording for the other LUN pages also. 
Am I missing something? 
Thanks, 
Kevin D. Butt
SCSI & Fibre Channel Architect, Tape Firmware
MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
Tel: 520-799-2869 / 520-799-5280
Fax: 520-799-2723 (T/L:321)
Email address: kdbutt at us.ibm.com
http://www-03.ibm.com/servers/storage/ 



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