00-213r0 -- SAM-2 Byte Count That’s Really Buffer Size

Ralph Weber ralphoweber at CompuServe.COM
Wed Apr 19 10:11:55 PDT 2000

* From the T10 Reflector (t10 at t10.org), posted by:
* Ralph Weber <ralphoweber at compuserve.com>
A proposal for consideration at the May meetings has
been placed on the T10 FTP site as:

< ftp://ftp.t10.org/t10/document.00/00-213r0.pdf >

The proposal contains figures and other features that cannot be
translated to ASCII for reflector distribution.  You will need to
download the PDF to review the proposal.

The proposal can be summarized as follows:

Doc:  T10/00-213r0
Date: 18 April 2000
To:   T10 Technical Committee
From: Ralph Weber (ENDL Texas)
Subj: SAM-2 Byte Count That's Really Buffer Size

During the letter ballot review of FCP-2 Crossroads comment #5 (see
1.5 in 00-150r1) requested that the FCP-2 definition of 'command byte
count' match the SAM-2 definition, which it referenced.

FCP-2 editor Bob Snively rejected this comment saying that the SAM-2
definition restricted the target's option to retry transferring some
or all of the data in response to appropriate error conditions
detected in the service delivery subsystem (okay, Bob said that Fibre
Channel detected the error, and I'm writing in SAMtalk). None the
less, Bobs observation is correct. The SAM-2 (and SAM) definition
shown above limits the target to transferring each byte in the
application clients data buffer exactly once.

During the working group review of this issue, a figure was
discovered in SAM-2 (and SAM) (SAM-2 rev 13 pdf page 70) that showed
'command byte count' as the application client data buffer size and
exactly the entity that FCP-2 wants to reference.

The working group agreed that SAM-2 should be changed to use the
'command byte count' concept shown in the figure, as opposed to the
written definition. This proposal contains a collection of specific
SAM-2 changes to meet the working group request.

This proposal replaces the 'command byte count' term with
'application client buffer size' and gives the new term a definition
that matches the figure and the needs of FCP-2. The term 'command
byte count' is not retrained because its connotations are not
compatible with the intent of the change.

Each occurrence of 'command byte count' in SAM-2 is discussed in this
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