Information field in (5-2100) -Reply

Mon Nov 18 17:13:08 PST 1996

* From the SCSI Reflector (scsi at, posted by:
> Which value is the correct response in
> Information byte of Sense Code(5-2100:Illegal
> Block Address out of Range) ?

> The answer is b). This is most useful to the
> initiator for learning what the correct range
> is, and this detail used to be specified in
> SCSI-2.

Another data point:

I've seen drives that return a small variation on
(b), namely: the max LBA of 25h read capacity PLUS

I never did run down WHY.

If I were a host guy, any time I wanted to know
the capacity I would issue a 25h read capacity -
and then I suppose probably still distrust the
existence of the last sector.  I've seen host
software disagree on exactly this point: they
disagree over how many MS-DOS "cylinders" to fake
for a drive in response to a capacity near a
multiple of the size of an MS-DOS cylinder.

As a drive guy, I choose weird capacities that
waste a few sectors.  Nobody honestly cares about
a few sectors in a billion, no matter how much
grief they give you.  And weird capacities avoid
this problem.

Might be worth mentioning that I've seen
vendor-specific stuff for moving around in other
address spaces (i.e. in z, theta, r space rather
than in LBA space) reuse 5h 21h 00h to mean
"invalid address", and then returns either garbage
or the maximum address value - WITHOUT the "plus

Or I might just be rambling. :)  You judge.

Cheers.   Pat LaVarre

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