Question:
How do I fix Diskettes With Bad Blocks?
Answer:
The traditional wisdom in trying to salvage bad diskettes is: don't. There's
a good reason not to if the cause of the bad diskette is bad block(s). A bad
block is a defect on the disk media's surface.
Do a disk verify in either Copy II+ v9.1 or the GSOS Finder and discover if
there are any bad blocks. The Finder tries 3(?) times to read a block and
will report an error if it can't; I'm not sure how many tries Copy II+ or ADU
makes. If any are found, discard the diskette.
Bad blocks that show up on hard drives aren't as critical as on diskettes.
R/W heads in a hard drive do not touch the surface of the HD's spinning
platters, where they do with a diskette. A bad block on a HD can be "mapped
out" safely during a low-level reformat or by using a separate utility with
that function. The Operating System and file I/O software will then know not
to access those blocks.
If you try that mapping out process with a diskette that has bad blocks, the
disk may last for a while, but eventually it will propagate more bad blocks
as the R/W head(s) "drag" across the diskette's surface and extend the damage
beyond the original bad blocks.
The idea to try and salvage "bad" diskettes may be economically preferable,
but the disks will eventually grow more bad blocks, destroying data in the
process. I can personally verify the sad truth of this, having lost the only
copy of several important files in the past.
As I was a subscriber to several diskette magazines and software of the month
clubs, the first thing I did was to verify each one and try to salvage as
much as possible onto tested-good diskettes whenever a bad block was
reported. About 5% of my subscriptions had bad blocks (the duplication
process slows waaaay down if a verify is required, so most didn't do it). The
salvage process usually did the trick, since most bad blocks were on unused
sections or in non-critical files.
