Re: iSCSI ERT: handling for iSCSI response codes

[julian_satran@il.ibm.com]

Steph,

That is an interesting change in opinion. When I suggested the same thing
some releases ago for the same set of reasons
(I even suggested avoiding the response codes at all!) as there is no
noticeable difference in handling the heat of your response was felt at
6000 miles.

However I am not sure anymore that given the need for a clearing action for
most of those cases that we should not keep
the treatment within the iSCSI layer and create an
iSCSI-exception-condition (for all iSCSI created responses) cleared through
an iSCSI task management function (clear-iSCSI-exception) and reject all
intervening commands.

This type of handling will let us build independent of SCSI and keep the
layering purists happy.

Regards,
Julo

Stephen Bailey <steph@cs.uchicago.edu> on 14-06-2001 05:42:09

Please respond to Stephen Bailey <steph@cs.uchicago.edu>

To:   cbm@rose.hp.com
cc:   Julian Satran/Haifa/IBM@IBMIL, someshg@yahoo.com,
      venkat@rhapsodynetworks.com, ldalleore@snapserver.com,
      Black_David@emc.com, John Hufferd/San Jose/IBM@IBMUS,
      kalman_meth@il.ibm.com
Subject:  Re: iSCSI ERT: handling for iSCSI response codes




Mallikarjun,

> Comments?

Hmm.  Ok, I agree.

For example, I never really thought:

>       0x02 - Delivery Subsystem Failure

was the right way to report in-band integrity errors.  Delivery
subsystem failure usually means something that is not even detectable
by the target, like a timeout.  As such, I agree that the target
shouldn't be responding this back.

Yes, I have seen many FCP targets do exactly what you're suggesting
here.  In fact 0xB 0x4700 (good ole SCSI parity error) is code for
many different protocol errors which are detectable and attributable
to a particular SCSI command.  For example, bogus settings of FCP
F_CTL bits.

So, assuming that Target Failure, Delivery Subsystem Failure are all
attributable to a SCSI command, I agree they should create CHECK
conditions.

The place where response values are justified is if the error is
attributable to something other than a SCSI command, such as a task
management function.  For example, task management function rejected
(which we don't seem to have).  If we were anticipating any of these
as a response to task management, they should remain, or perhaps we
should define new, more specifically task management related responses
codes.

I'm not clear on what you're proposing for SNACK rejected, but, since
it's not CHECK CONDITION, I'm sure whatever you have in mind is fine,
but we need to document it better :^)

Steph