Hi:
The behavior for immediate commands seems ambiguous and possibly
needlessly
complex.
Rev 06 says the following regarding ordered delivery to the SCSI layer:
"Except for the commands marked for immediate delivery the iSCSI
target layer MUST deliver the commands to the SCSI target layer in
the order specified by CmdSN. Commands marked for immediate delivery
may be handed over by the iSCSI target layer to the SCSI target layer
as soon as detected. iSCSI may avoid delivering some command to the
SCSI layer if so required by some prior SCSI or iSCSI action (e.g.,
clear task set Task Management request received before all the
commands it was supposed to act on)."
In a non-striped session consisting of one TCP/IP connection, the above
could be interpreted to allow the delivery of an immediate command before
other partly received commands that were previously issued. As a result,
an
operation, such as an abort task, might bypass the command to be aborted
--
even if both were sent on the same connection.
Assuming that's true, I believe a useful simplification is to require
that
all traffic flowing over a given TCP/IP connection be delivered to the
SCSI
layer in the order received over that connection. In a striped session,
an
immediate command might therefore leapfrog commands on other connections
but
would never bypass commands on the same connection. In my opinion, that
simplifies the problem of properly purging commands and stale PDUs in the
wake of a task management operation.
Charles
Charles Monia
Senior Technology Consultant
Nishan Systems
email: cmonia@nishansystems.com
voice: (408) 519-3986
fax: (408) 435-8385
