#: 20901 S12/OS9/68000 (OSK)
    10-Apr-95  22:00:51
Sb: #20900-Disk Junked?
Fm: David Breeding 72330,2051
To: Bob van der Poel 76510,2203 (X)

 > When this happens it is usually a good idea to make sure that everything
 > on the HD is backed up, reformat it, and restore all the data. Could be
 > that you have a sector acting up.

around with it today trying to get it to happen on my floppy.  Oh, it happened
again last night. (Make that Sunday, might not u/l this on Mon, when I'm
composing).. I had gone online abt. 10 PM.  Had composed a QWK reply, taking up
two 512-byte sectors + 1 for File Descr.  About 11PM began doing some more
zipping.. I was zipping severaly files, ranging from 40K - 600K (before
compression).  I wound up getting about 1.75 meg in file.. I did "zip -d" for a
few to get it down to fit in 1.44M floppy.  I _think_ a time or two, I had run
dcheck, can't remember exactly what I'd done..  Then I copied the file to a PC
disk.  I then del'ed the zip file.  Then I did dcheck had 3 sectors "not in
bitmap" - traced them to be the QWK reply.  I just "del'ed" that file and
everything was OK.

I don't think I had run dcheck immediately before copying to PC disk, but I'm
sure I had done it at times during the zipping, after my previous observations.
I suspect that somewhere along the way, "zip" walked right over the little
file, probably occupying a sector immediately below that file and then just
going right across it.  I'm beginning to suspect that the trouble might be in
zip with large files.  It writes temp files and it _could_ be it cheats or
something, possibly rewriting to the disk directory structure, but this is just
a guess.

I tried to duplicate the error staying strictly in the floppy, writing small
files and having plenty of fragmentation... Finally did get an error with
beaucoup "not in bitmap".  The only thing is that with my system, our floppies
are dreadfully slow.. Actually, when this error had occurred, I had rewritten a
device descriptor (/f0) and changed the step rate to 3 (6ms) hoping to get it
faster, so this could have been the prob.

 > If you just have one file which you can't read (due to a bad sector, etc)
 > it is easy to lock out the entire file (including the bad sector) by using
 > DED to set the first character in the filename in the directory to '0'.
 > That way the file disappears, but the storage remains allocated...at least
 > that way nothing else can use it.

So far, I've not had unreadable files as such, it's the bitmap that's getting
munged, I think mostly from files writing to the same sector. (The FD gets set
correctly, apparently, but the bitmap is not being followed correctly.

I feel it is either one of my programs (either zip or my PC disk driver) or my
system is writing to the disk when it is not positioned correctly.


                         -- David Breeding --
       CompuServe : 72330,2051             Delphi :  DBREEDING
    *** Composed with InfoXpress/OSK Vr. 1.02 & VED Vr. 2.4.0  ***