Re: Converted EXT4 is Slow to Check

From	Borax Man <boraxman@geidiprime.invalid>
Newsgroups	comp.os.linux.misc
Subject	Re: Converted EXT4 is Slow to Check
Date	2026-05-08 12:38 +0000
Organization	A noiseless patient Spider
Message-ID	<slrn10vrmaj.cs1.boraxman@geidiprime.invalid> (permalink)
References	(8 earlier) <slrn10vh4vv.2tn.boraxman@geidiprime.invalid> <n5sv1qFolppU2@mid.individual.net> <gjmdnU6EHePm6mT0nZ2dnZfqn_WdnZ2d@giganews.com> <slrn10vp423.92m.boraxman@geidiprime.invalid> <10tja2s$2gr2q$3@dont-email.me>

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On 2026-05-08, Lawrence D’Oliveiro <ldo@nz.invalid> wrote:
> On Thu, 7 May 2026 13:14:43 -0000 (UTC), Borax Man wrote:
>
>> The CRC gets copied with the file. You can archive with it as well,
>> so when you extract years later, you can still verify.
>
> What do you do if it fails to verify? This only helps if you have
> at least two archive copies.
>
> Rather than doing a single checksum for the whole file, do it for file
> sections. Because typically the corruption will only occur in one
> part, not across the whole file. And nowadays we use cryptographic
> hashes, as being a bit more thorough as an error check than old-style
> CRCs.
>
> To do it really robustly, you start to get into error-correcting codes
> and erasure codes. I think also Merkle trees could get involved at
> some point ...

If it fails you need to restore a good version.  At least you'll know
which version is good, if you have two copies and they differ for some
unknown reason, I wrote it a while ago, while BTRFS was still
"experimental".  I used to use sha1 or md5, but it was a bit cumbersome,
and felt it would be better to store the checksum in the file somehow
rather than have seperate files.

Doing it section by section doesn't help much if the tool can't repair
anyway, which mine doesn't.

If you want a robust system which can repair without a backup, you can
always use parchive, which can store parity data allowing you to check
AND repair up to a certain amount of damage.  However it doesn't work as
well for large directory trees, and if you do decide to 'parchive' a
whole folder, and you need to delete or update a file, you have to
compute it all again.

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Thread

Converted EXT4 is Slow to Check Leroy H <lh@somewhere.net> - 2026-04-24 00:04 +0000
  Re: Converted EXT4 is Slow to Check Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-04-24 02:29 +0000
    Re: Converted EXT4 is Slow to Check Leroy H <lh@somewhere.net> - 2026-04-24 09:23 +0000
      Re: Converted EXT4 is Slow to Check The Natural Philosopher <tnp@invalid.invalid> - 2026-04-24 10:28 +0100
      Re: Converted EXT4 is Slow to Check c186282 <c186282@nnada.net> - 2026-04-24 19:46 -0400
  Re: Converted EXT4 is Slow to Check "Carlos E.R." <robin_listas@es.invalid> - 2026-04-24 10:55 +0200
  Re: Converted EXT4 is Slow to Check Borax Man <boraxman@geidiprime.invalid> - 2026-04-26 12:53 +0000
    Re: Converted EXT4 is Slow to Check Leroy H <lh@somewhere.net> - 2026-04-26 14:01 +0000
      Re: Converted EXT4 is Slow to Check "Carlos E.R." <robin_listas@es.invalid> - 2026-04-26 20:54 +0200
      Re: Converted EXT4 is Slow to Check Borax Man <boraxman@geidiprime.invalid> - 2026-04-27 13:25 +0000
  Re: Converted EXT4 is Slow to Check Rich <rich@example.invalid> - 2026-04-27 15:24 +0000
    Re: Converted EXT4 is Slow to Check Borax Man <boraxman@geidiprime.invalid> - 2026-04-29 13:10 +0000
      Re: Converted EXT4 is Slow to Check Rich <rich@example.invalid> - 2026-04-29 15:57 +0000
        Re: Converted EXT4 is Slow to Check c186282 <c186282@nnada.net> - 2026-04-30 01:02 -0400
          Re: Converted EXT4 is Slow to Check "Carlos E.R." <robin_listas@es.invalid> - 2026-04-30 11:01 +0200
          Re: Converted EXT4 is Slow to Check Borax Man <rotflol2@hotmail.com> - 2026-04-30 12:36 +0000
            Re: Converted EXT4 is Slow to Check gazelle@shell.xmission.com (Kenny McCormack) - 2026-04-30 14:32 +0000
              Re: Converted EXT4 is Slow to Check Nuno Silva <nunojsilva@invalid.invalid> - 2026-04-30 16:42 +0100
                Re: Converted EXT4 is Slow to Check Borax Man <boraxman@geidiprime.invalid> - 2026-05-03 12:29 +0000
                Re: Converted EXT4 is Slow to Check "Carlos E.R." <robin_listas@es.invalid> - 2026-05-03 21:13 +0200
                Re: Converted EXT4 is Slow to Check Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-03 22:05 +0000
                Re: Converted EXT4 is Slow to Check jayjwa <jayjwa@atr2.ath.cx.invalid> - 2026-05-04 12:08 -0400
                Re: Converted EXT4 is Slow to Check John Bokma <contact@johnbokma.com> - 2026-05-04 19:24 +0200
                Re: Converted EXT4 is Slow to Check Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-05 00:00 +0000
                Re: Converted EXT4 is Slow to Check Borax Man <boraxman@geidiprime.invalid> - 2026-05-04 12:41 +0000
                Re: Converted EXT4 is Slow to Check "Carlos E.R." <robin_listas@es.invalid> - 2026-05-04 20:04 +0200
                Re: Converted EXT4 is Slow to Check Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-05 00:05 +0000
                Re: Converted EXT4 is Slow to Check "Carlos E.R." <robin_listas@es.invalid> - 2026-05-05 12:07 +0200
                Re: Converted EXT4 is Slow to Check Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-05 21:56 +0000
                Re: Converted EXT4 is Slow to Check "Carlos E.R." <robin_listas@es.invalid> - 2026-05-06 02:41 +0200
                Re: Converted EXT4 is Slow to Check Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-06 04:13 +0000
                Re: Converted EXT4 is Slow to Check Nuno Silva <nunojsilva@invalid.invalid> - 2026-05-06 13:03 +0100
                Re: Converted EXT4 is Slow to Check Richard Kettlewell <invalid@invalid.invalid> - 2026-05-06 10:21 +0100
                Re: Converted EXT4 is Slow to Check "Carlos E.R." <robin_listas@es.invalid> - 2026-05-06 13:36 +0200
                Re: Converted EXT4 is Slow to Check Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-06 21:16 +0000
                Re: Converted EXT4 is Slow to Check Nuno Silva <nunojsilva@invalid.invalid> - 2026-05-06 23:31 +0100
                Re: Converted EXT4 is Slow to Check Marc Haber <mh+usenetspam2616@zugschl.us> - 2026-05-07 06:41 +0200
                Re: Converted EXT4 is Slow to Check Nuno Silva <nunojsilva@invalid.invalid> - 2026-05-07 08:34 +0100
                Re: Converted EXT4 is Slow to Check Richard Kettlewell <invalid@invalid.invalid> - 2026-05-07 09:06 +0100
                Re: Converted EXT4 is Slow to Check "Carlos E.R." <robin_listas@es.invalid> - 2026-05-07 10:58 +0200
                Re: Converted EXT4 is Slow to Check not@telling.you.invalid (Computer Nerd Kev) - 2026-05-08 09:00 +1000
                Re: Converted EXT4 is Slow to Check Nuno Silva <nunojsilva@invalid.invalid> - 2026-05-08 09:45 +0100
                Re: Converted EXT4 is Slow to Check not@telling.you.invalid (Computer Nerd Kev) - 2026-05-09 10:01 +1000
                Re: Converted EXT4 is Slow to Check Leroy H <lh@somewhere.net> - 2026-05-09 00:12 +0000
                Re: Converted EXT4 is Slow to Check Computer Nerd Kev <not@telling.you.invalid> - 2026-05-09 17:30 +1000
                Re: Converted EXT4 is Slow to Check Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-08 00:12 +0000
                Re: Converted EXT4 is Slow to Check "Carlos E.R." <robin_listas@es.invalid> - 2026-05-08 10:57 +0200
                Re: Converted EXT4 is Slow to Check Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-08 09:26 +0000
                Re: Converted EXT4 is Slow to Check "Carlos E.R." <robin_listas@es.invalid> - 2026-05-08 12:47 +0200
                Re: Converted EXT4 is Slow to Check Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-08 21:55 +0000
                Re: Converted EXT4 is Slow to Check Nuno Silva <nunojsilva@invalid.invalid> - 2026-05-08 16:42 +0100
                Re: Converted EXT4 is Slow to Check Richard Kettlewell <invalid@invalid.invalid> - 2026-05-08 22:42 +0100
                Re: Converted EXT4 is Slow to Check Nuno Silva <nunojsilva@invalid.invalid> - 2026-05-09 08:34 +0100
                Re: Converted EXT4 is Slow to Check Richard Kettlewell <invalid@invalid.invalid> - 2026-05-09 10:18 +0100
                Re: Converted EXT4 is Slow to Check "Carlos E.R." <robin_listas@es.invalid> - 2026-05-09 13:31 +0200
                Re: Converted EXT4 is Slow to Check Marc Haber <mh+usenetspam2616@zugschl.us> - 2026-05-09 09:57 +0200
                Re: Converted EXT4 is Slow to Check c186282 <c186282@nnada.net> - 2026-05-06 00:53 -0400
                Re: Converted EXT4 is Slow to Check "Carlos E.R." <robin_listas@es.invalid> - 2026-05-06 10:47 +0200
                Re: Converted EXT4 is Slow to Check Borax Man <boraxman@geidiprime.invalid> - 2026-05-07 13:17 +0000
                Re: Converted EXT4 is Slow to Check rbowman <bowman@montana.com> - 2026-05-05 01:22 +0000
                Re: Converted EXT4 is Slow to Check c186282 <c186282@nnada.net> - 2026-05-05 00:52 -0400
                Re: Converted EXT4 is Slow to Check "Carlos E.R." <robin_listas@es.invalid> - 2026-05-05 12:11 +0200
                Re: Converted EXT4 is Slow to Check c186282 <c186282@nnada.net> - 2026-05-06 00:46 -0400
                Re: Converted EXT4 is Slow to Check rbowman <bowman@montana.com> - 2026-05-06 06:43 +0000
                Re: Converted EXT4 is Slow to Check c186282 <c186282@nnada.net> - 2026-05-06 11:05 -0400
                Re: Converted EXT4 is Slow to Check rbowman <bowman@montana.com> - 2026-05-06 19:47 +0000
                Re: Converted EXT4 is Slow to Check Bobbie Sellers <bliss-sf4ever@dslextreme.com> - 2026-05-06 15:10 -0700
                Re: Converted EXT4 is Slow to Check c186282 <c186282@nnada.net> - 2026-05-06 22:04 -0400
                Re: Converted EXT4 is Slow to Check rbowman <bowman@montana.com> - 2026-05-07 06:32 +0000
                Re: Converted EXT4 is Slow to Check c186282 <c186282@nnada.net> - 2026-05-07 17:37 -0400
                Re: Converted EXT4 is Slow to Check rbowman <bowman@montana.com> - 2026-05-08 00:30 +0000
                Re: Converted EXT4 is Slow to Check c186282 <c186282@nnada.net> - 2026-05-07 23:20 -0400
                Re: Converted EXT4 is Slow to Check "Carlos E.R." <robin_listas@es.invalid> - 2026-05-06 10:51 +0200
                Re: Converted EXT4 is Slow to Check The Natural Philosopher <tnp@invalid.invalid> - 2026-05-06 17:38 +0100
                Re: Converted EXT4 is Slow to Check "Carlos E.R." <robin_listas@es.invalid> - 2026-05-06 20:52 +0200
                Re: Converted EXT4 is Slow to Check Borax Man <boraxman@geidiprime.invalid> - 2026-05-07 13:14 +0000
                Re: Converted EXT4 is Slow to Check The Natural Philosopher <tnp@invalid.invalid> - 2026-05-07 16:51 +0100
                Re: Converted EXT4 is Slow to Check Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2026-05-07 18:35 +0000
                Re: Converted EXT4 is Slow to Check The Natural Philosopher <tnp@invalid.invalid> - 2026-05-07 20:08 +0100
                Re: Converted EXT4 is Slow to Check Borax Man <boraxman@geidiprime.invalid> - 2026-05-08 12:47 +0000
                Re: Converted EXT4 is Slow to Check The Natural Philosopher <tnp@invalid.invalid> - 2026-05-08 14:22 +0100
                Re: Converted EXT4 is Slow to Check Rich <rich@example.invalid> - 2026-05-08 13:24 +0000
                Re: Converted EXT4 is Slow to Check Borax Man <boraxman@geidiprime.invalid> - 2026-05-09 14:08 +0000
                Re: Converted EXT4 is Slow to Check "Carlos E.R." <robin_listas@es.invalid> - 2026-05-07 20:20 +0200
                Re: Converted EXT4 is Slow to Check Borax Man <boraxman@geidiprime.invalid> - 2026-05-08 12:40 +0000
                Re: Converted EXT4 is Slow to Check Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-08 00:17 +0000
                Re: Converted EXT4 is Slow to Check Borax Man <boraxman@geidiprime.invalid> - 2026-05-08 12:38 +0000
                Re: Converted EXT4 is Slow to Check Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-08 21:07 +0000
                Re: Converted EXT4 is Slow to Check Borax Man <boraxman@geidiprime.invalid> - 2026-05-09 14:06 +0000
                Re: Converted EXT4 is Slow to Check Rich <rich@example.invalid> - 2026-05-09 15:27 +0000
                Re: Converted EXT4 is Slow to Check Borax Man <boraxman@geidiprime.invalid> - 2026-05-10 12:28 +0000
                Re: Converted EXT4 is Slow to Check "Carlos E.R." <robin_listas@es.invalid> - 2026-05-05 12:08 +0200
              Re: Converted EXT4 is Slow to Check The Natural Philosopher <tnp@invalid.invalid> - 2026-04-30 17:05 +0100
                Re: Converted EXT4 is Slow to Check c186282 <c186282@nnada.net> - 2026-04-30 14:28 -0400
              Re: Converted EXT4 is Slow to Check Borax Man <boraxman@geidiprime.invalid> - 2026-05-03 12:15 +0000
            Re: Converted EXT4 is Slow to Check The Natural Philosopher <tnp@invalid.invalid> - 2026-04-30 16:54 +0100
            Re: Converted EXT4 is Slow to Check Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-05-01 00:15 +0000
              Re: Converted EXT4 is Slow to Check c186282 <c186282@nnada.net> - 2026-04-30 20:36 -0400
                Re: Converted EXT4 is Slow to Check Borax Man <boraxman@geidiprime.invalid> - 2026-05-03 12:08 +0000
      Re: Converted EXT4 is Slow to Check c186282 <c186282@nnada.net> - 2026-04-30 00:59 -0400

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