SAM UML and question about command priority and Task manager/device server

Kevin D Butt kdbutt at us.ibm.com
Mon Jun 9 14:20:09 PDT 2014


Formatted message: <a href="http://www.t10.org/cgi-bin/ac.pl?t=r&f=r1406094_f.htm">HTML-formatted message</a>

In the last SAM conference call, a couple of us were thinking that the 
command priority should not only be determined by the device server but 
also the task manager.
I was one of those who thought this.  I have since repented of that sin. 
;-) 
I now believe that allowing the task manager to be part of prioritizing 
the commands would actually break the model and it should not be allowed. 
After reviewing this internally, it was pointed out to me that the task 
manager must maintain proper serialization in some aspect if it is going 
to be able to properly manage task management functions.  Those TM 
functions need to be sent after the commands and not before.  This infers 
that the commands and task management functions must be serialized by the 
task manager (in some fashion).  If command priority were to be managed by 
the task manager, this would either break that model or at least make it 
much more complex.
Thanks,
Kevin D. Butt
SCSI Architect, Tape Firmware, T10 Standards
Data Protection & Retention
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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