14-176r0 - Including SIZE OF UNMAP REGION in UNMAP CDB

Gerry Houlder gerry.houlder at seagate.com
Thu Jul 3 07:30:07 PDT 2014


Formatted message: <a href="http://www.t10.org/cgi-bin/ac.pl?t=r&f=r1407030_f.htm">HTML-formatted message</a>

I am wondering what problem this will solve.
The drive can currently report, in VPD page B0h (Block Limits), the Maximum
Unmap LBA Count and Maximum Unmap Descriptor Count. The drive should be
able to accept any count that is less than these values or else the drive
is reporting a count that is too high. If a host takes notice of the VPD
page values and stays within the limits, then there should be no need for
this additional check (which the drive has to do by transferring all of the
descriptors and calculating whether the lengths of all of the descriptors
matches the new parameter).
The drive can do this instead -- calculate the length of all descriptors
and compare it to the maximum Unmap LBA count in the VPD page instead. This
doesn't require any new parameters.
Are you concerned about catching a rogue host that isn't paying attention
to the VPD page values and sends unmap lengths that are too large anyway?
Those hosts will just put zero in the size of unmap region field anyway, so
adding this check won't help with that.
On Wed, Jul 2, 2014 at 4:33 PM, Dave Landsman <Dave.Landsman at sandisk.com>
wrote:
>  It is advantageous in certain situations if a device knows the total
> length of a region being requested to be unmapped, before having to process
> the parameter data which describes the UNMAP data in detail.
>
>
>
> An enhancement to the UNMAP command is proposed.  Please see
> http://www.t10.org/cgi-bin/ac.pl?t=d&f=14-176r0.pdf.
>
> dave
>
> ------------------------------
>
> PLEASE NOTE: The information contained in this electronic mail message is
> intended only for the use of the designated recipient(s) named above. If
> the reader of this message is not the intended recipient, you are hereby
> notified that you have received this message in error and that any review,
> dissemination, distribution, or copying of this message is strictly
> prohibited. If you have received this communication in error, please notify
> the sender by telephone or e-mail (as shown above) immediately and destroy
> any and all copies of this message in your possession (whether hard copies
> or electronically stored copies).
>
>



More information about the T10 mailing list