Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uwm.edu!bionet!apple!mattd
From: mattd@Apple.COM (Matt Deatherage)
Newsgroups: comp.sys.apple
Subject: Re: Hard disk woes..
Message-ID: <39005@apple.Apple.COM>
Date: 27 Feb 90 00:43:14 GMT
References: <2080@orbit.cts.com>
Organization: Apple Computer Inc, Cupertino, CA
Lines: 41

In article <2080@orbit.cts.com> dougm@pnet51.orb.mn.org (Doug Mcintyre) writes:
>
>        Would someone from Apple or someone who has messed around a lot with
>the SCSI drivers and GS/OS care to comment on *exactly* what error conditions
>arrise to give the generic cryptic error message: Hard1 may be damaged?
>After getting out of the text box, Orca then complains directory structure
>damaged... I've looked around the directory structure, obviouslly it isn't
>damaged, and Orca just isn't up to the times, but what is wrong?
>

If directory structures were always "obviously" damaged, hard disk recovery
would be a lot easier.  I don't suppose you've done something really difficult
like use a professional disk diagnostic program (like Mr. Fixit in Prosel) to
verify that nothing is wrong?

The error in question ($51) comes when an FST has determined that something is
amiss in the directory.  The exact causes will vary from file system to file
system.  The ProDOS FST checks many things built into the disk structure that
ProDOS 8 normally leaves alone - forwards and backwards links in directories,
bitmap blocks matching physical blocks, blocks being doubly allocated, etc.
These things aren't guaranteed.

The most likely cause of a "damaged" directory that vanishes when you go to P8
is memory trashing.  The ProDOS FST normally caches directory blocks, and if
someone trashes them in memory it will detect a "damaged" directory structure
when it tries to read.  It will actually damage the directory if it tries to
write a trashed block to disk.  You might try running the Prosel disk repair
utility under Prosel 16 and then under Prosel 8.  If problems are present with
the former and absent with the latter, I'd bet someone's stomping on the cache.

>
>UUCP: {rosevax, crash}!orbit!pnet51!dougm               Compuserve: 70611,2215
>ARPA: crash!orbit!pnet51!dougm@nosc.mil                      ALPE: DougMac
>INET: dougm@pnet51.cts.com                                   GENIE: D.MCINTYRE1

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Matt Deatherage, Apple Computer, Inc. | "The opinions represented here are
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