Comments on 05-177r0 "write same"

Sheffield, Robert L robert.l.sheffield at
Wed May 4 14:05:40 PDT 2005

* From the T10 Reflector (t10 at, posted by:
* "Sheffield, Robert L" <robert.l.sheffield at>

The SAT WG agreed that whether the SATL issues an SCD LBA Segment Access
command is contingent on whether the device reports in IDENTIFY DEVICE
that it supports SCD LBA Segment Access. The SAT standard cannot base
any standard requirements on vendor-specific or out-of-band controls
that might modify what a device supports or not, so it is not
appropriate to specify SATL behavior with respect to whether or not SCT
LBA Segment Access or SCD (in general) is "enabled". Any coordination
between a SATL with regards to vendor-specific enable/disable of these
features is, of course, vendor-specific, and not documented in the


-----Original Message-----
From: owner-t10 at [mailto:owner-t10 at] On Behalf Of
James.C.Hatfield at
Sent: Wednesday, May 04, 2005 12:47 PM
To: curtis.stevens at
Cc: t10 at
Subject: RE: Comments on 05-177r0 "write same"

* From the T10 Reflector (t10 at, posted by:
* James.C.Hatfield at
You are correct in stating that there is no documented standard
way to 'enable or disable' SCT LBA Segment Access, but there <is> a
documented way for the device to separately report that
     a) it supports (or not) SCT (in general)     <and>
     b) is supports (or not) SCT LBA Segment Access

It is vendor unique whether or not there is a way to change the settings
of these bits.

Please refer to the SCT Technical report (1701DT rev 5, page 5)
      IDENTIFY DEVICE, word 206
      bit 0 = SCT Feature set supported (includes SCT status)
      bit 2 = LBA Segment Access (AC2) supported

I request that the SAT document needs to address what to do if bit 0 is
to one
and bit 2 is cleared to zero.

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

(from Curtis Stevens' notes of the discussion at the SAT meeting May 3

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

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

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
the LBA Segment Access subcommand) enabled?

Committee Response:
      There is enable/disable for SMART, but there is no enable or
for SCT.

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