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From: diamond@jit533.swstokyo.dec.com (Norman Diamond)
Newsgroups: comp.sys.mips
Subject: Re: bad block tables lost?
Message-ID: <1991May16.060214.22997@tkou02.enet.dec.com>
Date: 16 May 91 06:02:14 GMT
References: <91May15.232155edt.20146@me.utoronto.ca>
Sender: usenet@tkou02.enet.dec.com (USENET News System)
Reply-To: diamond@jit533.enet@tkou02.enet.dec.com (Norman Diamond)
Organization: Digital Equipment Corporation Japan , Tokyo
Lines: 31

In article <91May15.232155edt.20146@me.utoronto.ca> sun@ME.UTORONTO.CA (Andy Sun) writes:

>I worked on an M/1000 that has lost its original defect
>list (i.e. bad sector table). The documentation said the scanning phase
>of format.std will pick out the bad sectors, but apparently it didn't,
>not all of them anyways (it got 15 out of 212). Everytime I installed the
>OS back, I got this "sector not found" error and I haven't a clue what's
>going on. Finally, after entering the manufacturer's defect list + the
>disk scanning, this problem finally disappeared. I don't see any point
>in this so-called "scanning" phase, especially it is a time-consuming
>process and it's actually going through each cylinder.

Disks deteriorate over time.  The purpose of the scanning process is to
find sectors that have become bad since the last time they were used.

Manufacturers have equipment to perform harsher tests than a normally
operating disk drive can do, so they detect borderline blocks that would
pass scanning tests.  This is why they provide an initial list in the
first place.  It is generally considered better to avoid using a block
that seems relatively likely to go bad within a few years, rather than
use it until it goes bad (with loss of data).  So these are generally
disabled even when scanning and usage would (temporarily) work.

Nonetheless, if the scanning process passed a sector that produced
"sector not found" a short time later, I'd say the scanning process is
far from adequate.
(This does not represent the opinion of my employer or any other organization.)
--
Norman Diamond       diamond@tkov50.enet.dec.com
If this were the company's opinion, I wouldn't be allowed to post it.
Permission is granted to feel this signature, but not to look at it.