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Re: Schrödinger's hash

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On 2026-05-22 at 11:53, Charles Curley wrote:

> Starting about a week ago, the script finds an error in one or more 
> files out of several. Results are inconsistent: one pass may find an 
> error in a given file, the next pass not find any errors in it.
> Running checksums manually, one at a time, does not turn up an error.
> Running "tar tvf" finds no error in a suspect file. Running "bunzip2
> -t" also turns up no error. Only running the script turns up any
> errors.
> 
> I create two checksum files when I create the backups, for sha256
> and sha512. After this problem surfaced (about a week ago), I then
> made two new checksum files of a suspect file. The two checksum file
> pairs (e.g. both sha512sum files) show the same checksums. The script
> now tests using both the old and new checksum files. Sometime only
> one pair of checksum files fail the suspect file.
> 
> In addition to all of that, I also get the occasional "bad message" 
> error. I have no idea what that means, but an fsck seems to deal
> with it.

Just for clarity: where (from what source), and when (at what point), is
it that you get this error?

> To be thorough, I have run extended SMART tests on the hard drives, 
> kicked mdadm into testing the RAID array, and fscked the LVM
> partitions on the RAID array. Only fsck turned up issues, and that
> has not stopped.

> I have a hypothesis as to what is going on, but would like to hear
> from you before I discuss it.

The very first thing that came to my mind out of that was RAM issues.
Disk issues was the second, but the tests you've run there seem as if
they'd probably have ruled that out.

If you run a script to generate the hash of a given file in a loop
(possibly with a don't-overload-the-system pause in between if you
prefer), does it always show the same hash, or does it sometimes show a
different one?

-- 
   The Wanderer

The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore all
progress depends on the unreasonable man.         -- George Bernard Shaw

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Schrödinger's hash Charles Curley <charlescurley@charlescurley.com> - 2026-05-22 18:00 +0200
  Re: Schrödinger's hash Andrew Latham <lathama@gmail.com> - 2026-05-22 18:10 +0200
    Re: Schrödinger's hash Charles Curley <charlescurley@charlescurley.com> - 2026-05-22 18:20 +0200
      Re: Schrödinger's hash Andrew Latham <lathama@gmail.com> - 2026-05-22 18:30 +0200
        Re: Schrödinger's hash Charles Curley <charlescurley@charlescurley.com> - 2026-05-22 19:00 +0200
    bad RAM (Was: Schrödinger's hash) nwe <nwe@gitcoding.net> - 2026-05-22 19:40 +0200
      Re: bad RAM (Was: Schrödinger's hash) Charles Curley <charlescurley@charlescurley.com> - 2026-05-22 22:10 +0200
        Re: bad RAM (Was: Schrödinger's hash) nwe <nwe@gitcoding.net> - 2026-05-22 22:30 +0200
          Re: bad RAM (Was: Schrödinger's hash) Charles Curley <charlescurley@charlescurley.com> - 2026-05-22 23:10 +0200
            Re: bad RAM (Was: Schrödinger's hash) nwe <nwe@gitcoding.net> - 2026-05-22 23:30 +0200
          Re: bad RAM (Was: Schrödinger's hash) David Christensen <dpchrist@holgerdanske.com> - 2026-05-23 02:00 +0200
  Re: Schrödinger's hash The Wanderer <wanderer@fastmail.fm> - 2026-05-22 18:20 +0200
    Re: Schrödinger's hash Charles Curley <charlescurley@charlescurley.com> - 2026-05-22 19:10 +0200
  Re: Schrödinger's hash David Christensen <dpchrist@holgerdanske.com> - 2026-05-22 20:10 +0200
  Re: Schrödinger's hash Van Snyder <van.snyder@sbcglobal.net> - 2026-05-22 20:40 +0200
    Re: Schrödinger's hash nwe <nwe@gitcoding.net> - 2026-05-22 21:50 +0200
      Re: Schrödinger's hash David Christensen <dpchrist@holgerdanske.com> - 2026-05-23 01:30 +0200
        Re: Schrödinger's hash Van Snyder <van.snyder@sbcglobal.net> - 2026-05-23 01:40 +0200
        Re: Schrödinger's hash nwe <nwe@gitcoding.net> - 2026-05-23 02:20 +0200
          Re: Schrödinger's hash David Christensen <dpchrist@holgerdanske.com> - 2026-05-23 07:50 +0200
            Home server (Was: Re: Schrödinger's hash) nwe <nwe@gitcoding.net> - 2026-05-23 17:00 +0200
              Re: Home server (Was: Re: Schrödinger's hash) David Christensen <dpchrist@holgerdanske.com> - 2026-05-24 04:30 +0200

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