Subject: Re: iSCSI: current UNH Plugfest

From: "Julian Satran" <[email-masked]>
Date: Thu, 1 Nov 2001 12:11:57 +0200

Anshul,

IMHO a single MUST in the paragraph is strong enough and covers all the 
cases.

Julo

"Anshul Chadda" <[email-masked]>
Sent by: [email-masked]
31-10-01 19:34
Please respond to "Anshul Chadda"

        To:     <[email-masked]>
        cc: 
        Subject:        Re: iSCSI: current UNH Plugfest

Hello:
As this issue has come up with setting CHECK CONDITION in the SCSI 
Response. It is assumed that if CHECK CONDITION is set in the SCSI 
Response PDU, then there has to be sense data accompanied with it. So as 
far as I see it, it would help if the following sentence in the draft has 
the MUST/must in there. In the current wording, i can think that if there 
is no data segment in the SCSI Response PDU for a CHECK CONDITION, it is 
still OK.
 
In draft 8, the sentence looks like the following: 
-------------------------------------------------------
3.4.6 Data Segment - Sense and Response Data Segment
iSCSI targets MUST support and enable autosense. If Status is CHECK 
CONDITION (0x02), then the Data Segment contains sense data for the failed 
command.
-------------------------------------------------------
 
It can be changed to the following:
 
-------------------------------------------------------
3.4.6 Data Segment - Sense and Response Data Segment
iSCSI targets MUST support and enable autosense. If Status is CHECK 
CONDITION (0x02), then the target MUST have sense data in the data segment 
for the failed command.
-------------------------------------------------------
I don't know if there is a reason that the draft has the wording in the 
current way.  Apologies if this subject has already been discussed. 
 
Regards,
Anshul
 
-----------------------------------------------------------------------------------------------------------------
 
5. Some common error situations:

   1) - when a SCSI Response contains a CHECK CONDITION (Status=0x02),
      some targets are not including the SenseLength as the first 2
      bytes in the data segment.  Although the format of the data segment
      is clear from the diagram in section 3.4.6 on page 62 of draft 8
      (page 63 of draft 8a), the last entry in the diagram for the SCSI
      Response PDU on page 58 of draft 8 (page 59 of draft 8a) is
      misleading because it mentions only the Sense Data and Response
      Data and omits the Sense Length.  It would therefore be helpful
      if the last entry in the diagram on page 58 were changed to 
explicitly
      reference the diagram on page 62, as in:

         Data Segment -- see section 3.4.6 (optional)

---

From: "Robert D. Russell" <[email-masked]>
Date: Thu, 1 Nov 2001 09:50:04 -0500

Julian:

IMHO if we mean MUST then we MUST say MUST.

It is clear from the exchange between Anshul, Santosh and Robert
that we already have different interpretations of what
it means without MUST and hence we have interoperability problems.

In this particular case I agree with Anshul and Robert that the
standard should say MUST.  Santosh's argument that in an error
case the data gets lost does not seem to be relevant --
in error cases lots of information gets lost and recovery is
necessary to get that information back.  The spec provides for
this.  We should not be introducing interoperability problems
because of a situation that may arise in the rare case of an error,
especially when the spec already deals with recovery of that
information when the error is detected.

Thanks,

Bob Russell
InterOperability Lab
University of New Hampshire
[email-masked]
603-862-3774