Arbitration Fairness Control proposal
Robert Elliott
relliott at hobbit.eng.hou.compaq.com
Thu Apr 1 14:14:48 PST 1999
* From the T10 Reflector (t10 at symbios.com), posted by:
* relliott at hobbit.eng.hou.compaq.com (Robert Elliott)
*
T10/99-160r0 is now on the web site. This is on the agenda
for next week's SPI-3 meeting and (unless changed) will be on
the May SCSI working group meeting (for the SPC-2/FCP-2 changes).
A summary follows:
We propose controlling the arbitration fairness algorithm with
the Disconnect-Reconnect mode page (2h) by making these changes:
* Redefine the three FA bits as a ARBITRATION FAIRNESS field, to
be defined by the protocol standards
* In FCP-2, define the field as three bits:
FARd, FAWrt, FASel (same as before)
* In SPI-3, for normal arbitration, define 000b as unfair and
001b - 111b as fair
* In SPI-3, for quick arbitration, define the field as "drop down
to normal arbitration every Nth time the device wins quick
arbitration." This will help QAS performance when non-QAS devices
are not expected to be present.
See the document for details. Any comments before the meeting
are welcome.
--
Rob Elliott UNIX mailto:relliott at hobbit.eng.hou.compaq.com
Houston, TX PC mailto:Robert.Elliott at compaq.com
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