Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!iuvax!cica!gatech!hubcap!rwberry
From: rwberry@hubcap.clemson.edu (Robert W Berry)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Disk Problem
Message-ID: <6159@hubcap.clemson.edu>
Date: 3 Aug 89 23:46:51 GMT
References: <16031@pasteur.Berkeley.EDU>
Distribution: na
Organization: Clemson University, Clemson, SC
Lines: 45

From article <16031@pasteur.Berkeley.EDU>, by chao@cory.Berkeley.EDU (Chia-Chi Chao):
> ... 
> 1. Disk #1 with some files, say File1 and File2 -- write protected.
>    Disk #2 with File3 and File4 -- not write-protected.
> 2. Copy File5 to Disk #1 -- but intended for Disk #2.
> 3. DOS reports write-protect error -- Abort, Retry, Fail?
> 4. Swap Disk #1 with Disk #2 and use Retry.
> 5. Disk #2 ends up with unuseable File1 and File2 headers and good File5.
>    File3 and File4 are no longer recognized.
> 
> I understand that the problem is in writing the FAT of Disk #1 onto Disk #2
> without recognizing that the disk was changed.  Is there a patch to eliminate
> this problem in DOS (I assume that's the problem), or I just have to be more
> careful?

Sounds like you have experienced the famous DOS buffers dork (FDBD!!!).
Check your config.sys file and look for the line
     BUFFERS=XX
where XX is some integer.  This is a (painfully) limited caching system
that DOS uses to speed up disk accesses.  Unfortunately, if DOS caches
the FAT and you switch disks, then DOS will write back the updated FAT
whenever it has to dump the cache for other information.  End result: a
diskette with the FAT of one disk and the data sectors of another.

You don't have this problem if you are using a fixed disk (since you
can't switch media while the FAT is in cache.)  

I've seen countless disks trashed this way (although I thought the
problem was fixed as of MS-DOS 3.2) usually belonging to well-meaning
neophytes trying to tweak a little more performance out of their PC.

I generally tell people not to use the BUFFERS option in their
config.sys, or if they must have a cache, to use a reputable third party
caching program such as DiskQuick of PC-Cache.

> 
> Thanks for any information.    Chia-Chi    chao@cory.berkeley.edu

Hope this helps, (tm)
Bob
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