Re: Mac HD volume corruption under GS/OS

[nathan@visi.com (Nathan Mates)]

In article <3405E2EB.6C6@ahml.lib.il.us>,
AHML Patron  <ahmlpub@ahml.lib.il.us> wrote:
>Since ProDOS can only support volumes of up to 32K, and SCSI can
>only have seven volumes, the last partition on my hard drive is
>formatted for the Macintosh.

   [Nitpick: 32MB :] Also, SCSI is limited to 7 physical *devices*,
not partitions. The Apple HS SCSI allows up to 127 or so partitions;
the RamFAST about 14. If you're using ProDOS 8, you will have a
limitation of at most 14 (realistically about 10 if you have 5.25" or
3.5" drives in the system) of those volumes online at once. 

>Now to the question: Occasionaly, I have experienced problems writing to
>the mac volume. It either causes my computer to go to the text screen
>flashing "Detected trashed memory-software bug or (less likely) bad RAM"
>or gives me a "generic FST error".

   The first message is just that: something's trashed memory due to
either a software bug or bad RAM. I'd advise checking out the RAM to
make sure it's all functional. For memory trashing, I'd advise making
sure you're running with all the latest patches (Blatang Plug Follows
:) Grand Unified Patch Program (GUPP) written by myself, contains
fixes for many problems in System 6.0.1 and other programs. It's
available at all the usual legitimate Apple II ftp sites; see the csa2
FAQ at http://www.visi.com/~nathan/a2/faq/csa2.html

   Also, check out what inits/das/CDevs/etc you're running. It's
possible that one of them is buggy and causing memory
trashing. Another of my programs, MessageChecker, watches another set
of important system memory structures to detect signs of trashing.

   I've never seen the second error message appear when working with
HFS, but it may be a side effect from the first, or something.

>Copying everything off the volume, reformatting it from the Finder,
>then copying everything back clears it up, but is a real pain. Does
>the fix for the Mac FST mentioned in the CSA2 FAQ fix this problem,
>and do I now need to copy everything off again and put it all back?

   In my opinion, possibly not. As the FAQ notes, the patch only
applies to HFS volumes >96MB in size. As I understand it, the default
6.0.1 HFS FST miscalculates (but at least consistently) where blocks
end up on the disk. Thus, files can overwrite each other and a bunch
more rather insidious problems-- your files can still be read, but
they may be scrambled internally. The fix does recommend copying off
all the data (using the consistently wrong access to make sure that
all files are read, even if they're trashed), installing the fix, and
then copying back (using the hopefully consistently correct access).

   If you were to install the fix without copying files off, then
the new file reading routines may not go to the same places that the
files were originally [mis]written to.

>I also don't get on Internet every day, or every week, so please
>don't delete the response for at least a month.

   As the csa2 FAQ notes, your reading of usenet is maintained by a
*LOCAL* administrator.  Policies for article expiration are set by
them; talk to them if you want anything changed.

Nathan Mates
--
<*> Nathan Mates http://www.visi.com/~nathan/      <*>
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