Write those again please, encoded how

Gerry Houlder gerry.houlder at seagate.com
Tue Aug 24 15:06:48 PDT 2010


Formatted message: <a href="http://www.t10.org/cgi-bin/ac.pl?t=r&f=r1008242_f.htm">HTML-formatted message</a>

Yes, you are correct that there is no existing answer for a drive to tell an
initiator that there are more LBAs than just the ones in the command that
failed that also are bad. Once that many LBAs go bad, the host has to switch
to a backup copy in order to restore the data anyway or else maybe the data
is gone forever (no backup copy). I suspect that most hosts would treat the
lost of several Gigabytes of data as a catastrophic error, worthy of never
trusting that drive to store data ever again.
On Tue, Aug 24, 2010 at 12:42 PM, Pat LaVarre <p.lavarre at ieee.org> wrote:
> * From the T10 Reflector (t10 at t10.org), posted by:
> * Pat LaVarre <p.lavarre at ieee.org>
> *
> Given this paradox:
>
> a) Often SSD's include spare capacity to raise the apparent 'endurance'
> of how many times the host can rewrite the sector at an LBA.
>
> b) Such SSD's can suddenly unexpectedly lose all the gigabytes of a
> whole chip die & still keep on running if the host rewrites all those
> lost LBA’s by remapping those LBA's to other dies.
>
> c) T10 SBC requires such SSD's to refuse to READ any lost sector,
> instead returning a KCQ such as:
>
> 311C3h MEDIUM ERROR/ UNRECOVERED READ ERROR - VENDOR-SPECIFIC 311C3H
> 3110Ch MEDIUM ERROR/ UNRECOVERED READ ERROR - RECOMMEND REWRITE THE DATA
> 31103h MEDIUM ERROR/ MULTIPLE READ ERRORS
> 31100h MEDIUM ERROR/ UNRECOVERED READ ERROR
>
> Then I ask:
>
> Q: What signal(s) should the drive send to suggest the host rewrite all
> the LBA's of the lost die?
>
> Merely refusing to read the lost sectors, or even all sectors, doesn't
> just work. Many hosts don't then efficiently find this middle ground of
> rewriting just the lost die, instead hosts waste much time by trying
> each lost sector individually or by actually returning the drive for
> service.
>
> Is there no existing answer? Inventing an entirely new answer of course
> wastes time in waiting for the hosts to catch up and implement it.
>
> Thanks in advance,
>
>
> *
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