Format Unit SI bit

Penokie, George George.Penokie at
Tue Jun 7 09:01:56 PDT 2011

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You are both right and wrong.
What happen when the SI bit is set depends on the customers specification. Is
some cases the intent may that the device be totally inoperable (think the
helicopter and all electronics need to be destroyed). In less radical
conditions the drive may come back usable with data scrubbed off.
At the time this was put in there was no agreement by the committee as to how
scrubbed the data had to be, again that was intended to be left up to the
customers specification.
Bye for now,
George Penokie
LSI Corporation
3033 41st St. NW
Suite 100
Rochester, MN 55901
george.penokie at
From: owner-t10 at [mailto:owner-t10 at] On Behalf Of Gerry Houlder
Sent: Tuesday, June 07, 2011 10:18 AM
To: T10 Reflector
Cc: Truong Nguyen - SISA
Subject: Re: Format Unit SI bit
I think Mark's interpretation is too broad. The SI bit is intended to trigger
a vendor specific security initialize feature. Things the device has to do to
implement this take precedence over other bits that might specify conflicting
demands. However things that specify the required final format (e.g., logical
block size, FMTPINFO) and whether existing defect lists are included or not
(e.g., FMTDATA, CMPLST, DEFECT LIST FORMAT, defect list length) should still
be obeyed. If an initialization pattern is specified, that should be the
pattern left on the media after the security initialize is complete. The SI
bit probably affects how defective areas (i.e., areas excluded from the user
data area) are treated, but should not cause the device to ignore
instructions about which areas are to be handled as defective areas.
On Fri, Jun 3, 2011 at 10:56 AM, Mark Evans
<Mark.Evans at> wrote:
Hi Truong,
The SI bit was added into the INITIALIZATION PATTERN DESCRIPTOR for the
FORMAT UNIT command in SBCr-05 based on proposal 96-186R1.  As you wrote the
definition of the bit was modified slightly in SBC-r06 as the result of
discussion at the SCSI working group meetings in October of 1996.  The
definition of the SI bit has not been changed since that time.
What I think we really intended the new wording to mean is, "If the SI bit
its set to one, then the device server shall ignore:
a)	 the FMTPINFO field;
b)	the FMTDATA bit;
c)	 the CMPLST bit;
d)	the DEFECT LIST FORMAT field;
e)	 all of the bits and fields in the parameter list header, except the
IMMED bit; and
f)	  any defect list data.
Others may correct me if I'm wrong.  You know who you are, and I'm sure you
will - ha!
Please feel free to call or send an email to me with any comments or
questions that you have about this stuff.
Mark Evans
Western Digital Corporation
5863 Rue Ferrari
San Jose, CA 95138
Email: mark.evans at
From: owner-t10 at<mailto:owner-t10 at>
[mailto:owner-t10 at<mailto:owner-t10 at>] On Behalf Of Truong
Nguyen - SISA
Sent: Thursday, June 02, 2011 5:54 PM
To: t10 at<mailto:t10 at>
Subject: Format Unit SI bit
In SBC3r27, in the Format Unit initialization pattern descriptor subclause, there is a statement regarding the SI bit precedence:
"An SI bit set to one shall take precedence over any other FORMAT UNIT CDB
What is this statement supposed to mean specifically?
It seems as though the statement was added some time ago in SBCr6:
"Clarified SI by adding the statement An SI bit set to one shall take
precedence over any other FORMAT UNIT field."
I could not find any proposals associated with the modification.
Truong Nguyen
Samsung Information Systems America

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