From: Hugo Mills <hugo@carfax.org.uk>
To: Timofey Titovets <nefelim4ag@gmail.com>
Cc: linux-btrfs <linux-btrfs@vger.kernel.org>
Subject: Re: Does btrfs use crc32 for error correction?
Date: Tue, 19 Sep 2017 15:40:16 +0000 [thread overview]
Message-ID: <20170919154016.GA8264@carfax.org.uk> (raw)
In-Reply-To: <CAGqmi74kxPpkuYCBwfdyzxUKAHE6TP9x1FGDz0FURud21u=nOA@mail.gmail.com>
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On Tue, Sep 19, 2017 at 06:35:48PM +0300, Timofey Titovets wrote:
> Stupid question:
> Does btrfs use crc32 for error correction?
It uses it for error _detection_. On read, it'll verify the data
(or metadata) against the checksum.
With no reduncancy (single, RAID-0), a bad csum check will return
I/O error.
With redundancy (RAID-1, 10, 5, 6), a bad csum check will try
reading the other copy. If that's good, it will use it and repair the
broken copy.
Hugo.
> If no, why?
>
> (AFAIK if using CRC that possible to fix 1 bit flip)
>
> P.S. I try check that (i create image, create text file, flip bit, try
> read and btrfs show IO-error)
>
> Thanks!
--
Hugo Mills | Dullest spy film ever: The Eastbourne Ultimatum
hugo@... carfax.org.uk |
http://carfax.org.uk/ |
PGP: E2AB1DE4 | The Thick of It
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next prev parent reply other threads:[~2017-09-19 15:40 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-19 15:35 Does btrfs use crc32 for error correction? Timofey Titovets
2017-09-19 15:40 ` Hugo Mills [this message]
2017-09-19 16:51 ` Eric Sandeen
2017-09-19 18:04 ` Marat Khalili
2017-09-20 1:52 ` Timofey Titovets
2017-09-20 22:04 ` Timofey Titovets
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