Comments on 05-177r0 "write same"

Curtis Stevens curtis.stevens at wdc.com
Wed May 4 12:24:18 PDT 2005


* From the T10 Reflector (t10 at t10.org), posted by:
* "Curtis Stevens" <curtis.stevens at wdc.com>
*
Jim

	Your E-Mail was discussed during SAT and these are the responses
|from the committee:

1. OPCODE - Is there a preferred hierarchy of choices for implementation?
If a device does not support SCT, is there a preference for the other 2
choices?

Committee Respose: 
	a. Wording was changed to reference SCT LBA Segment Access.  There
is no enable or disable for this capability.

	b. There is a reference to clause 9.12.2 which presents a hierarchy
of recommendations for write commands.

2. Is it worth putting "(NCQ)" next to the term "WRITE FPDMA QUEUED"?
Committee Response: We removed the command list from the opcode description.

3. Please clarify the meaning of "device implements SCT".  See 1a above.

4. What if the ATA device (target) 'supports' SCT, but does not have it (or
the LBA Segment Access subcommand) enabled?
Committee Response: There is enable/disable for SMART, but there is no
enable or disable for SCT.

5. Please change the SCT reference from  Long Segment Access to LBA Segment
Access
Committee Response: Agreed

6. Please add a reference to the SCT technical report to the 'References
under development' section of the main SAT document.
Committee Response: Agreed

7. PBDATA and LBDATA - ATA devices typically do not support protection
information.  Please mark these fields as U = Unimplemented.
Committee Response: These fields will be marked as E (for Emulated) with
some explanation that the SATL is responsible for intercepting the data and
managing the fields as defined in SBC-2 and issueing write commands.

8. NUMBER OF BLOCKS
8.1 Mark this field as E = Emulated
Committee Response: Agreed

8.2 "...If the NUMBER OF BLOCKS is not zero, the SATL shall write the number
of sectors specified to the device."

                  Please change the wording to clarify:
                  a) The SATL will only write ONE block to the device,
                        as sent to it by the initiator
                  b)  This field indicates how many blocks starting from
                        LOGICAL BLOCK ADDRESS are to be written
                        with the single sector of data from the initiator.

Committee Response: Curtis will wordsmith to make more clear.

8.3 ..."if the NUMBER OF BLOCKS field is greater ..."

a) This seems to be a very awkward way of saying that if the LOGICAL BLOCK
ADDRESS plus the NUMBER OF BLOCKS is greater than the largest LBA supported
by the device then the SATL may terminate the command can some better
wording be chosen?
Committee Response: This statement was deleted from the text.

b) Watch for devices that support 48-bit LBAs, but do not have 48-bit mode
enabled, and for devices that do not support 48-bit LBAs at all.
Curtis Response: 9.12.2 gives the hierarchy for write command support.  I do
not know how 48-bit can be supported but not enabled.

c)    "... the SATL may terminate..."
Committee Response: This statement was struck from the document.  It is up
to the SATL to determine how the error is generated.
 
-------------------------------------------------
Curtis E. Stevens
20511 Lake Forest Drive #C-214D
Lake Forest, California 92630
Phone: 949-672-7933
Cell: 949-307-5050
E-Mail: Curtis.Stevens at WDC.com
Ambition is a poor excuse for not having enough sense to be lazy.
 
-----Original Message-----
From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of
James.C.Hatfield at seagate.com
Sent: Monday, May 02, 2005 4:09 PM
To: t10 at t10.org; Curtis Stevens
Subject: SAT: Comments on 05-177r0 "write same"

* From the T10 Reflector (t10 at t10.org), posted by:
* James.C.Hatfield at seagate.com
*
I am unable to attend the SAT meeting this week, but would like to comment
on
SAT proposal 05-177r0 regarding 'write same' translation.

I would greatly appreciate a reply (separate from the minutes) from the SAT
group regarding
the outcome of the discussion of this proposal.

Thank You !!!
-----------------------------------------------------------------
Jim Hatfield
Seagate Technology LLC
   e-mail:  James.C.Hatfield at seagate.com
   s-mail:  389 Disc Drive;  Longmont, CO 80503 USA
   voice:  720-684-2120
   fax....:  720-684-2711
==========================================


field       comment
----------------------
------------------------------------------------------------------------
OPCODE      Is there a preferred hierarchy of choices for implementation ?
            If a device does not support SCT, is there a preference
                  for the other 2 choices ?

            Is it worth putting "(NCQ)" next to the term "WRITE FPDMA
QUEUED" ?

            Please clarify the meaning of "device implements SCT".
            a)  What if the ATA device (target) 'supports' SCT, but does
not
                  have it (or the LBA Segment Access subcommand) enabled ?

            Please change the SCT reference
                  from  Long Segment Access
                  to    LBA Segment Access

            Please add a reference to the SCT technical report to the
            'References under development' section of the main SAT
document.

WRPROTECT
            ATA devices typically do not support protection information.

            This field is correctly marked as U = Unimplemented

PBDATA and LBDATA
            ATA devices typically do not support protection information.

            Please mark these fields as U = Unimplemented

GROUP NUMBER
            This field is correctly marked as U = Unimplemented

NUMBER OF BLOCKS
            1)    Mark this field as E = Emulated

            2)    "...If the NUMBER OF BLOCKS is not zero, the SATL shall
                  write the number of sectors specified to the device."

                  Please change the wording to clarify:
                  a) The SATL will only write ONE block to the device,
                        as sent to it by the initiator
                  b)  This field indicates how many blocks starting from
                        LOGICAL BLOCK ADDRESS are to be written
                        with the single sector of data from the initiator.

                  This is consistent with the SCT LBA Segment Acccess
commmand,
                  and with the obsolete ATA 'write same' command.

            3)    ..."if the NUMBER OF BLOCKS field is greater ..."

                  a) This seems to be a very awkward way of saying that if
                        the LOGICAL BLOCK ADDRESS plus the NUMBER OF BLOCKS
                        is greater than the largest LBA supported by the
device
                        then the SATL may terminate the command

                        Can some better wording be chosen ?

                  b)    Watch for devices that support 48-bit LBAs, but do
not have
                        48-bit mode enabled, and for devices that do not
support 48-bit LBAs at all.

                  c)    "... the SATL may terminate..."

                        i)   How about something more deterministic like
'shall' ?

                        ii)  or is it the responsibility of the ATA device
to check itself and
                              terminate a bad request from the SATL ?


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