Arbitration Fairness Control proposal

Robert Elliott relliott at
Thu Apr 1 14:14:48 PST 1999

* From the T10 Reflector (t10 at, posted by:
* relliott at (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    
Houston, TX        PC mailto:Robert.Elliott at
* For T10 Reflector information, send a message with
* 'info t10' (no quotes) in the message body to majordomo at

More information about the T10 mailing list