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