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Re: [PATCH] dtas-archive: paranoid archival script

From: Eric Wong
Subject: Re: [PATCH] dtas-archive: paranoid archival script
Date: Fri, 18 Sep 2015 08:54:01 +0000

Eric Wong <address@hidden> wrote:
> +dtas-archive is intended for archiving audio data to/from laptops and
> +computers without ECC memory, attempting to read data multiple times in
> +an attempt to detect memory corruption.  dtas-archive may only be
> +effective on machines running the Linux kernel where posix_fadvise(2)
> +can be used to drop caches for a particular file after fsync(2).
> +dtas-archive spawns sox(1) to archive audio data (likely uncompressed
> +WAVE) to FLAC and verifies the result using sndfile-cmp(1), a tool
> +implemented by different than sox and less likely to share the same bugs
> +(if any) as sox.

Fwiw, I'm VERY happy to note this script actually just detected an error
the kernel + ECC RAM did not notice.  The sox wav-to-flac copy was
corrupted, and sndfile-cmp caught the error after dropping the cache and
re-comparing.  I tried remounting the device just in case, but running
sndfile-cmp by hand reproduced the error.

Again, this was from my workstation with ECC memory, even, so the error
probably happened on the USB or device level.  I was just copying a WAV
file recording from a MicroSD card off a USB card reader.

Fwiw, I've been doing this cache-dropping + sndfile-cmp dance for nearly
3 years, now (with a different, unpublished script) now and this is my
first time detecting a real error.

I haven't listened, but stats off the corrupt copy did indicate

So the paranoia with verifying copies really is justified :>

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