Read Long Conundrum

PATRICK.L.SULLIVAN at cdev.com PATRICK.L.SULLIVAN at cdev.com
Sun Oct 2 10:07:51 PDT 1994


  I read with great interest Gene Milligan's comments on the potential
conflicts with the error
 recovery page and the Read Long command.  I am one who would feel agony if
this
command were deleted.  It is not uncommon for drives to not report data
errors which
 they were able to correct with on-the-fly ECC, no matter how the PER bit
is set.  It is
difficult to detect that a drive is doing this "favor" for you without the
Read/Write Long
commands.

I prefer Gene's third option (retraction of the working group
recommendation). Some
explicit language would be helpful, along the lines of his text for the
fourth option.  I have
heard people argue that the phrase "read without any correction made by the
target" for
CORRCT=0 means the target should not even attempt to detect errors.  Some
clarification
of target behavior would be useful.

 I was confused by his "editor's note":

>1. Unrecoverable (by re-reads and off-sets)  but Correctable ECC error,
CORRCT = 0:
>         a.  TB=0: Return  CHECK CONDITION status and the sense key set to
MEDIUM ERROR
>         with an additional sense code of  UNRECOVERED READ ERROR.
> (Editors Note: Since the user of the READ LONG command has written the data on
 purpose
> with the error and expects the data to be not corrected they on equally valid
grounds return
>uncorrected data and report a Good status with no associated
>sense.)

The note seems to say the command should terminate with Good status, and
associated
sense of NO SENSE, but the description prior to the note is the opposite.
Did some text
get dropped, or I am missing the obvious?

--
Pat Sullivan
patrick.l.sullivan at cdev.com
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