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.
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