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

Kevin D Butt kdbutt at us.ibm.com
Wed Sep 12 15:06:10 PDT 2007


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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



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