[T10] Comments on 19-066r0 SPC-5 SBC-4 Add rules for multi-LUN command interlock

Kevin D Butt kdbutt at us.ibm.com
Mon Jun 10 11:32:44 PDT 2019


It seems to me that your proposal changes the behavior 11b of the MLU 
field such that it is not backward compatible and removes an option that 
is currently available -- and perhaps is relied on. There will no longer 
be a way to affect all logical units with a single command. Now, each and 
every logical unit must be connected and communicating before the command 
can process. This includes the SANITIZE command. Now, in a critical 
situation where a device needs sanitized in a hurry, there are additional 
requirements that might not be met before the sanitize can occur.

The entire meaning of code 10b is changed.
This command affects more than one but not all logical units contained in 
this SCSI target device. This command operates on only this logical unit 
but may impact the performance of other logical units attached to this 
SCSI target device while this command is in progress. 
The new meaning relates solely to performance, while the original has no 
specification of what the effects might be.

Also, I am not sure the replacement of "affects" with "operates on" works 
as intended. There is a subtle difference which may cause issues.
Take "This command affects operates on only this logical unit. " This 
states that the command only operates on this logical unit, but it makes 
no statement  about whether or not it might cause effects to be noticed on 
other logical units.

Aside from the obvious changes, Code 11b changes from "logical units 
contained in" to "logical units attached to ".  Now the SCSI Target device 
must become a copy manager and forward that command to other logical units 
in other SCSI Target devices to which it may be attached.

SPC-5 SBC-4 Add rules for multi-LUN command interlock
(by: Gerald Houlder)
T10/19-066r0   Uploaded: 2019/06/04   135997 bytes

Kevin D. Butt
SCSI Architect, Tape Firmware, Data Retention Infrastructure
T10 Standards
MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
Tel: 520-799-5280
Fax: 520-799-2723 (T/L:321)
Email address: kdbutt at us.ibm.com

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