iSCSI Autosense

[Ralph Weber <ralphoweber@compuserve.com>]

Note: Clause numbers reference draft-satran-iscsi-01.txt.

There is nothing in the SCSI Architecture that requires the A
Flags bit (byte 2 bit 7) described in 3.2 and 3.2.1.  Specifically,
the SCSI Architecture does not require a transport to have the
ability to disable Autosense.

Contingent Allegiance (the target state that follows a CHECK
CONDITION in the absence of Autosense) is not a required SCSI
behavior.  In fact, Contingent Allegiance is an out dated
SCSI behavior that continues to be documented in SAM for
backwards compatibility.  Contingent Allegiance is wholly
superseded by the Autosense capability.

Autosense is dramatically simpler to implement provided the
SCSI transport protocol allows for delivery of the sense data
in the same packet as the CHECK CONDITION status (as is the
case in iSCSI).

IMHO iSCSI would be well served by following the precedent
set by FCP.  Remove the A bit and state explicitly that all
iSCSI devices are required to support Autosense and that
all instances of a CHECK CONDITION status shall be accompanied
by Autosense data.

Note: These changes will also affect 3.3.7, 5.3 and possibly
other clauses of the internet draft.

Thanks.

Ralph...