Re: Question: EMI Shielding for IDE cables
From: blue (user_at_host.com)
Date: 08/20/04
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Date: Fri, 20 Aug 2004 15:55:29 GMT
"Bob Masta" <NoSpam@daqarta.com> wrote in message
news:4125ebab.1243555@news.itd.umich.edu...
> On Thu, 19 Aug 2004 13:55:45 GMT, "blue" <user@host.com> wrote:
>
> <snip>
> >
> >The reason why I think it is interference of some sort:
> >I did some checking of a bunch of corrupt files in a hex editor. I
actually
> >had chunks of text from other text files. So data got scrambled up during
> >read/writes to the drives.
>
> The fact that you are seeing chunks of text from *other* files
> indicates that the FAT is screwed up. If your problem was
> transmission errors which somehow made it past the error correction
> stuff (which I think is not too likely, but possible), then you would
> have erroneous data in the file you sent. Most likely it would just
> look like garbage, or random byte replacements. I can't see any
> way that it could be parts of other files, barring some otherworldly
> interaction between parallel cables on 2 drives during simultaneous
> writes. Not likely!
>
> Of course, the FAT on the drive is also written by the same process
> that writes the rest of the file. So it's *possible* that some kind
> of noise pickup could corrupt the FAT data as it was updated. There
> are 2 copies of the FAT, so if they both are identical I'd say that
> was proof the trouble was somewhere else, in software. If it was
> noise in transmission, they would be different.
>
> If your drives use something other than FAT, like NTFS, then
> the same reasoning applies. But I don't know if or where they
> maintain a 2nd copy.
>
> Best regards,
>
>
>
>
>
> Bob Masta
> dqatechATdaqartaDOTcom
>
> D A Q A R T A
> Data AcQuisition And Real-Time Analysis
> www.daqarta.com
Actually seeing a chunk of recognizable data was a very rare occasion.
Here's how i found the chunk of text. I renamed some large directories of
archives, giving all the extension *.txt. I did a search on these files for
a specific string (my email address). I went to sleep, and the next day, the
search had found a file. I opened this in a hex editor, and sure enough,
there was my email address with a small chunk of text from an ancient email
in there. There is absolutely no reason why a solid data archive should have
this string, but it did happen, in one file of many.
This occured once, late in the game, after chkdsk had rewritten my index
files, so i'm not sure if this had anything to do with it. I did make
attempts to recover the ntfs index. I mirrored the entire drive with ghost,
and ran a recovery program from a boot disk. I got nothing useful from this
except more chkdsk madness on reboot after recovery. I think that a
scrambled up file index would have the off chance probablilty of referencing
incorrect data sectors for a file.
I only did this search once, on files that had been verified as corrupt. It
was out of curiosity (or madness) only, and didn't really have any purpose.
Keith
creekchubbAThotmailDOTcom (replace AT with @, and DOT with .)
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