On Sun, Dec 03, 2000 at 02:51:02PM +0000, Thomas Ribbrock wrote:
> Now - does anybody happen to know how these drives could be "self healing"?
SCSI drives (if they have not always been, they certainly have been for a
long time) are "self healing". SCSI drives do not expose their internal
layout to the outside world, presenting themselves instead as a big box of
data blocks (as you can see from 'dev 08:21, sector 2496262').
When the disk itself detects an impending media error e.g. if it has to
re-read a block to get its data it will put the data from that block onto
another block and will remap that block internally. I'm not sure here, but I
presume a media error gets returned from a SCSI disk when it can't manage to
do this remapping i.e. the first time it detects a problem, it's fatal as
you can see from the wording of the error message
sense key Medium Error
Additional sense indicates Unrecovered read error
> I mean, I probably still won't use them for anything really important (at
> least not until after at least a dozen more badblocks and other stress
Not sure that I'd ever use them for anything important :-)
> runs...), but I'd be curious to know how this works...
Hope this has assuaged your curiosity. I'm sure somebody can pick holes it,
but it's definitely close enough for government work.
Regards,
Niall
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