Re: Does btrfs use crc32 for error correction?

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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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