From: dplatt@ntg.com (Dave Platt)
Newsgroups: comp.sys.mac.system
Subject: Re: File copy unsuccessful -- what to do?
Date: 28 Dec 92 03:08:56 GMT
Organization: New Technologies Group, Inc.  Palo Alto CA

>Often when I try to copy a few files to a disk more than a month old, I
>get a message (in Finnish; can't give you the exact English wording but
>you'll recognize this one) telling me that the copy operation was
>unsuccessful, and offering me the options to either Cancel the copying
>or Continue. 
> ...
>I was under the impression that System 7 would handle these cases more
>gracefully. 

System 7 checks floppy disks for Badness when the floppies are
formatted.  Bad blocks are locked out - in effect they are marked as
being "owned by" a file which is inaccessible through the normal catalog
mechanisms.

System 7 does not attempt to add newly-discovered bad blocks to the
lockout file when the disk is in use.  If new areas of the disk go bad,
reformatting the disk is the only [standard] way I know of to lock them
out.

>With my limited understanding of the Mac file system, I'd guess
>+some+ innovative and good-hearted person should have come up with a
>utility which will scan the unused portions of the disk and flag the
>unusable sectors as bad in the allocation table (whatever it's called on
>a Mac disk). Question is, what? Where? How? 

This was possible even back under System 6 - I recall a utility called
Floppy Fixer which would do just this.  It didn't, as I recall, use the
System 7 "inaccessible file" mechanism to hide the bad blocks - I
believe it creates an ordinary file at the root of the directory, and
then makes it invisible.

I don't know whether the System 7 bad-block mechanism is set up in a way
which would permit newly-discovered bad blocks to be added to the
lockout file.

>Any other thoughts on this topic would be most valued.

Good-quality floppies, used in a clean well-maintained Mac floppy drive,
should not be developing bad blocks with any regularity.  The fact that
you're being hit by this problem so often suggests that [1] you may be
using a poor grade of floppy disk, or [2] your diskette drive may be out
of repair, or dirty.

Watch out for cheap "bargain" diskettes - they are often very expensive
in the long run.  Every time I buy "bargain" diskettes - even those
which are "100% certified" - I end up regretting it.  Of the last batch
of 20 cheap diskettes I bought, about 15 of them (75!) had to have bad
blocks mapped out during System 7 initialization - one of them had 200k
(!!) of bad surface area.  I took them back for a refund.  I've found
KAO and Fuji diskettes to be excellent, Sony to be OK, and Verbatim to
be quite poor.

Also - watch out for cigarette smoke.  It'll be sucked into the floppy
drive slot, and will coat the read/write heads with a sticky and
difficult-to-remove tar which will really foul up the mechanism.
Tobacco smoking should not be allowed near any computer with a floppy
disk drive (or a tape drive, for that matter).

-- 
Dave Platt                                                VOICE: (415) 813-8917
              Domain: dplatt@ntg.com      UUCP: ...netcomsv!ntg!dplatt
 USNAIL: New Technologies Group Inc. 2470 Embarcardero Way, Palo Alto CA 94303
Newsgroups: comp.sys.mac.system