SPC-4: Self Describing Command Timeouts (05-284r2)
Kevin D Butt
kdbutt at us.ibm.com
Sat Aug 5 22:05:33 PDT 2006
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A new version of my "self-describing" command time-outs has been posted.
This is a major revision from the one posted last November. I have a few
issues to solve that I would appreciate help with. The main one being how
to sufficiently address or skirt the delay injected by the time in the
My thoughts and experience are in the tape realm, and I don't have a good
feel for disk or enclosure or MMC. In the tape realm, reservations are
often used to ensure that only one host is doing data I/O (or time
intensive activities) at a time. While multiple host may be talking to
the drive, most are just polling to see if it is there or if it is
available (i.e. doesn't have an active reservation). In this scenario,
the command time-outs as I have described them will solve a high
percentage of the issues related to unknown command time-outs. The delay
injected by the queue (or the command(s) in the queue prior to this one)
do not often have an effect on the host doing data I/O.
Anyway, I need to understand better the issues seen by the other device
types. I would also appreciate any suggestions.
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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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