Re: question to btrfs scrub

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

On 2023/6/29 16:26, Bernd Lentes wrote:
> Hi guys,
>
> i have a BTRFS volume which produces a lot of errors in the syslog.
> Here I got the recommendation to start a “btrfs scrub” on that volume.
> I made an image of that volume (with dd) and started the scrub on that.
> That’s the result:
>
> ha-idg-1:/mnt/sdc1/ha-idg-1/image # btrfs scrub start -B /mnt/image/
>
> scrub done for bbcfa007-fb2b-432a-b513-207d5df35a2a
> Scrub started:    Tue Jun 27 20:47:26 2023
> Status:           finished
> Duration:         35:39:48
> Total to scrub:   5.07TiB
> Rate:             40.16MiB/s
> Error summary:    csum=1052
>    Corrected:      0
>    Uncorrectable:  1052
>    Unverified:     0
> ERROR: there are uncorrectable errors
>
> 1052 checksum errors on a 5TB volume. Is that much, or is that normal ?

I believe it's not normal, but please also provide the following info:

- Kernel version
- SMART info
- HDD model

> What can I do ?

You can check the dmesg, which should mention the file name of the
offending inode.

IIRC there used to be some bug causing csum mismatch, if it's all in one
file, you can backup and remove the file, then set nodatacow for that file.

> Start a btrfs check ?

It would never hurt, but if it's only csum errors, I believe btrfs check
would not report any major problem.

> First on the image before on the original ?

Yeah, on the image first.

Thanks,
Qu
>
> Thanks.
>
>
> Bernd Lentes
>
> --
> Bernd Lentes
> System Administrator
> MCD
> Helmholtzzentrum München
> +49 89 3187 1241
> mailto:bernd.lentes@helmholtz-munich.de
> https://www.helmholtz-munich.de/en/mcd
>
>
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