Fun with the Bad Block Table

[DoN Nichols]

In article <1991Feb15.231011.19453 at cbnewsc.att.com> cmv at cbnewsc.cb.att.com (C M Votava) writes:
>Helpful hint:

	[ ... text deleted ... ]

>
>OK, maybe sector 10 really means sector 11, so I un-bad-block sec 10 and
>bad-block sec 11. Still no good...rats! Well, after diddling around for a
>couple of days with this garbage, I finally did something that bad-blocked
>BOTH sectors 10 and 11... THAT WORKED! Just to double-check, I took each
>out one at a time and re-verified... they BOTH have to be marked as bad
>blocks to get rid of that nasty HDERR message.
>
>Anybody know why??? I don't.

	Well, one consideration is that the unix-pc uses 512 byte PHYSICAL
sectors on the hard drive, and 1K LOGICAL blocks from within the system.  It
takes two physical sectors to make one logical block.  When you map out a
bad sector, it replaces it with a nearby sector, usually sector 17 from that
track.  However, if you have both physical sectors bad from a block, the
system may give up on reading a block when the first sector fails, and never
even TRY the second sector of the block.  (I don't have source, so this is
just a guess).

	Anyone who knows more of the internals have a better answer?

	Good Luck with the drive
		DoN.
-- 
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