From: daveh@cbmvax.commodore.com (Dave Haynie)
Newsgroups: comp.sys.amiga.misc
Subject: Re: Disk validating in 2.0 ??
Date: 18 Dec 92 06:28:16 GMT
Reply-To: daveh@cbmvax.commodore.com (Dave Haynie)
Organization: Commodore, West Chester, PA

In article <1992Dec6.204823.16044@netcom.com> fuzzy@netcom.com (Fuzzy Fox) writes:
>jmpierce@whale.st.usm.edu (Jimmy Malcolm Pierce) writes:

>>       Chkdsk /f only checks the FAT table, not all sectors of the disk.

>That's because 99% of the problems on the disk are with the logical file
>system, not the physical disk media.  If the computer crashes during a
>disk write, it does NOT cause the physical disk media to become screwed
>up and require a format.  All that is needed is to reset the logical
>pointers of the file system so that everything matches up.  

There are a few things you'd like to have happen after a disk crash.  The
first is what CHKDSK does and DiskDoctor should have done, which is simply
to restore logical disk integrity such that the disk's filesystem can run
properly.  This isn't all that difficult.  At the very least, you have your
program walk through a disk's tree and remove anything that doesn't pass
an appropriate validity test.  The Amiga's "validator" does a very, very
primitive version of this, but it doesn't do anything that would require the
removal of possibly useful information.  

That leads to the other stuff you might want to do.  There's no telling what
a disk crash might have damaged.  You might lose one file or several.  If
you're really good at backups, a CHKDSK may be all you need.  More 
realistically, you've got stuff out there that's important.  I've had DiskSalv
users tell me of weeks worth unbacked stuff they managed to recover.  A
CHKDSK utility doesn't help here at all, and it may actually make the problem
worse by destroying information that a real recovery (rather than "fix-up")
program can use to do its best job at recovering lost information.  Actually,
that's much more possible on FAT style filesystems than Amiga filesystems,
but again, anything can happen during a disk crash.

>>My boss has told me that the only real way to fix an ms-dos disk is to use
>>Norton, or similar utilities. Myself, I use QBTools to fix my Amiga floppies.

>Your boss has succumbed to the same media hype that makes Amiga people
>spit out the automatic phrase, "You gotta use QB Tools; it's the way it
>was Meant To Be."  CHKDSK fixes nearly all problems on MS-DOS.  I am
>surprised that Commodore has not written a simple HD-fixing tool that
>will do the same thing for AmigaDOS volumes.

It's far from trivial to write a full featured disk recover program.  I've been
working on it on and off for nearly seven years.  Once you decide to do anything
more with a bad block than simply remove it from your directory tree, you're
talking about lots of clever code.  There is a reason ole Peter Norton built
a business out of doing basically this thing for you.  If you haven't run across
a problem CHKDSK doesn't fix, you're just plain lucky.  Though I do agree that
the Amiga should have at least a basic fix-up program included with the OS
release.  One that you can't trust is worse than none at all (the decision they
made for 2.1).

>That's my point:  MS-DOS does NOT required anything at all; Norton has a
>prettier interface and explains things better about what's going on, but
>it is not NEEDED.  It is just nice to have.

You may need Norton for some operations.  You don't for the trivial stuff.

-- 
Dave Haynie / Commodore Technology, High-End Amiga Systems Design (cool stuff)
 "The Crew That Never Rests"  {uunet|pyramid|rutgers}!cbmvax!daveh   BIX: hazy
		SCIENCE:	"I'll believe it when I see it"  
		RELIGION:	"I'll see it when I believe it"

Newsgroups: comp.sys.amiga.misc