Request for SCSI Working Group Agenda Item -- Problem with non-interlocked busses

Charles Monia monia at am.shrmsg.shr.mts.dec.com
Fri Oct 20 10:17:07 PDT 1995


Hi:

While reviewing S2P, the SSA SCSI protocol spec, I came across a problem that's
generic to any non-interlocked bus. Specifically, all such busses need some way to
flush in-transit SCSI commands and restart the command pipeline whenever a command
terminates with a BUSY, RESERVATION CONFLICT or QUEUE FULL status.

The problem is that, since all of the above conditions are transient and may
spontaneosly disappear, subsequent commands from that initiator which are in the
pipeline may be accepted by the logical unit, resulting in out-of-order command
execution.

It seems to me that, as a minimum, changes to SAM are required. More importantly,
changes to the non-interlocked protocol specs, such as FCP and SBP, may also be
needed.

In any event, I request that this item be added to the November SCSI Working Group
agenda for discussion.

Regards,
Charles Monia




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