[T10] WRITE SAME and 0 LBA counts

Ralph Weber roweber at ieee.org
Mon May 23 09:19:01 PDT 2016


The requested proposal is available as:
http://www.t10.org/cgi-bin/ac.pl?t=d&f=16-168r0.pdf

All the best,

.Ralph

On 5/23/2016 8:28 AM, George Penokie wrote:
> One persons "editorial" change could be another persons "substantive" 
> change. That said the fact that this thread is as long as it is means 
> to be that any change in this area will require a proposal.
>
> Bye for now,
> George Penokie
>
> Broadcom Limited
> Attn: George Penokie
> 4109 Manor View Dr NW
> Rochester , MN 55901
>
> 952-921-2495 <tel:952-921-2495>
> george.penokie at broadcom.com <mailto:george.penokie at avagotech.com>
>
> On Sun, May 22, 2016 at 5:30 PM, Black, David <david.black at emc.com 
> <mailto:david.black at emc.com>> wrote:
>
>     > That said, however, it would appear that the two quoted SBC-4 text
>     > citations profoundly violate T10's "say it the same way everywhere"
>     > strong recommendation (i.e., rule).
>
>     Indeed they do ...
>
>     > Therefore ...
>     >
>     > Although I cannot support adding "computed" anywhere, I see no
>     reason
>     > why the SBC-4 editor cannot step in, pick a single phrase to
>     describe
>     > the quantity, and cause that phrase to be used consistently.
>     >
>     > In the event that the SBC-4 editor decides to solicit guidance
>     from this
>     > reflector, my vote is for the wording with "contiguous" and
>     "requested"
>     > in it.
>
>     I concur with this suggestion.
>
>     Thanks, --David
>
>     > -----Original Message-----
>     > From: t10-bounces at t10.org <mailto:t10-bounces at t10.org>
>     [mailto:t10-bounces at t10.org <mailto:t10-bounces at t10.org>] On
>     Behalf Of Ralph
>     > Weber
>     > Sent: Saturday, May 21, 2016 7:34 AM
>     > To: t10 at t10.org <mailto:t10 at t10.org>
>     > Subject: Re: [T10] WRITE SAME and 0 LBA counts
>     >
>     > Looking only at the SBC-4 text fragments quoted by David Black,
>     I can
>     > find no place where adding the word "computed" will serve any
>     purpose
>     > other than an increase in confusion.
>     >
>     > That said, however, it would appear that the two quoted SBC-4 text
>     > citations profoundly violate T10's "say it the same way everywhere"
>     > strong recommendation (i.e., rule).
>     >
>     > One citation talks about "the number of contiguous logical
>     blocks that
>     > are requested to be unmapped or written".
>     >
>     > The other citation says "the number of logical blocks specified
>     to be
>     > unmapped or written".
>     >
>     > David can freely drop the "contiguous" and substitute
>     "specified" for
>     > "requested", but (when the case is put this plainly) I'll bet
>     steam will
>     > begin to emanate from George's ears (to name just one of the rule's
>     > proponents).
>     >
>     > Therefore ...
>     >
>     > Although I cannot support adding "computed" anywhere, I see no
>     reason
>     > why the SBC-4 editor cannot step in, pick a single phrase to
>     describe
>     > the quantity, and cause that phrase to be used consistently.
>     >
>     > In the event that the SBC-4 editor decides to solicit guidance
>     from this
>     > reflector, my vote is for the wording with "contiguous" and
>     "requested"
>     > in it.
>     >
>     > All the best,
>     >
>     > .Ralph
>     >
>     > On 5/21/2016 12:08 AM, Sitsofe Wheeler wrote:
>     > >
>     > >
>     > > On 19 May 2016 at 02:08, Black, David <david.black at emc.com
>     <mailto:david.black at emc.com>
>     > > <mailto:david.black at emc.com <mailto:david.black at emc.com>>> wrote:
>     > >
>     > >     As for the original question:
>     > >
>     > >     >When the spec says "number of logical blocks specified to
>     be [...]
>     > >     written" is this only in reference to the NUMBER OF
>     LOGICAL BLOCKS
>     > >
>     > >     > passed in rather than the computed number of blocks to
>     be written or is
>     > there a choice over which is used
>     > >     (i.e. the target can pick
>     > >
>     > >     > whether it errors or not if the computed blocks exceed
>     the MAXIMUM
>     > WRITE SAME LENGTH)?
>     > >
>     > >     Neither - my reading of the current SBC-4 text is that the
>     limit
>     > >     always applies to the number of blocks written by the
>     command, but
>     > >     a careful reading of the text is involved to reach that
>     > >     conclusion.  Excerpts that follow are from 5.47 WRITE SAME
>     (10) in
>     > >     SBC-4 rev 10:
>     > >
>     > >     If the WSNZ bit is set to zero, then a NUMBER OF LOGICAL
>     BLOCKS
>     > >     field set to zero specifies that the number of
>     > >
>     > >     contiguous logical blocks that are requested to be unmapped or
>     > >     written includes all of the logical blocks
>     > >
>     > >     starting with the LBA specified in the LOGICAL BLOCK
>     ADDRESS field
>     > >     to the last logical block on the medium.
>     > >
>     > >     Note the use of "specifies" in the first line.
>     > >
>     > >     If the number of logical blocks specified to be unmapped or
>     > >     written exceeds the value indicated in the
>     > >
>     > >     MAXIMUM WRITE SAME LENGTH field(see 6.6.4), then the
>     device server
>     > >     shall
>     > >
>     > >     terminate the command with CHECK CONDITION status with the
>     sense
>     > >     key set to ILLEGAL REQUEST and
>     > >
>     > >     the additional sense code set to INVALID FIELD IN CDB.
>     > >
>     > >     Note the use of "specified" in the first line.
>     > >
>     > >     So, a NUMBER OF LOGICAL BLOCKS field set to zero specifies
>     that
>     > >     all of the logical blocks up to the end of the medium are
>     to be
>     > >     unmapped or written, and if that (computed) number of logical
>     > >     blocks exceeds the MAXIMUM WRITE SAME LENGTH value, the
>     required
>     > >     result is CHECK CONDITION, ILLEGAL REQUEST, INVALID FIELD
>     IN CDB.
>     > >
>     > >     >For example, if I have an *SBC-3* 1GByte target with a
>     WSNZ of 0
>     > >     and a MAXIMUM WRITE SAME LENGTH of 131072 blocks
>     > >
>     > >     > (64Mbytes with a sector size of 512), then I issue a
>     WRITE SAME with
>     > NUMBER OF LOGICAL BLOCKS of 0 and a
>     > >
>     > >     > LOGICAL BLOCK ADDRESS of 0 is it legal for the SBC-3
>     target to produce an
>     > error because the computed number of
>     > >
>     > >     > blocks to be written will be greater than 131072?
>     > >
>     > >     That is not only "legal", it is also the behavior required
>     by the
>     > >     standard.
>     > >
>     > >     I believe the standard is unambiguous as written, but I'd
>     support
>     > >     an editorial clarification to reduce the degree of careful
>     reading
>     > >     required to reach that conclusion.
>     > >
>     > >
>     > > The minor clarifications (where you added the word "computed" in
>     > > brackets) were helpful and I'd say it would be helpful in the
>     spec.
>     > > Whatever happens thanks for clearing up the only acceptable
>     behaviour!
>     > >
>     > > --
>     > > Sitsofe | http://sucs.org/~sits/ <http://sucs.org/%7Esits/>
>     <http://sucs.org/%7Esits/>
>     > >
>     > >
>     > > _______________________________________________
>     > > T10 mailing list
>     > > T10 at t10.org <mailto:T10 at t10.org>
>     > > http://www.t10.org/mailman/listinfo/t10
>     >
>     > _______________________________________________
>     > T10 mailing list
>     > T10 at t10.org <mailto:T10 at t10.org>
>     > http://www.t10.org/mailman/listinfo/t10
>
>     _______________________________________________
>     T10 mailing list
>     T10 at t10.org <mailto:T10 at t10.org>
>     http://www.t10.org/mailman/listinfo/t10
>
>



More information about the T10 mailing list