Re: degraded BTRFS RAID 1 not mountable: open_ctree failed, unable to find block group for 0

[Martin Steigerwald <martin.steigerwald@teamix.de>]

Am Mittwoch, 16. November 2016, 11:55:32 CET schrieben Sie:
> So mounting work although for some reason scrubbing is aborted (I had this
> issue a long time ago on my laptop as well). After removing /var/lib/btrfs 
> scrub status file for the filesystem:
> 
>     merkaba:~> btrfs scrub start /mnt/zeit
>     scrub started on /mnt/zeit, fsid […] (pid=9054)
>     merkaba:~> btrfs scrub status /mnt/zeit
>     scrub status for […]
>             scrub started at Wed Nov 16 11:52:56 2016 and was aborted after 
> 00:00:00
>             total bytes scrubbed: 0.00B with 0 errors
> 
> Anyway, I will now just rsync off the files.
> 
> Interestingly enough btrfs restore complained about looping over certain
> files… lets see whether the rsync or btrfs send/receive proceeds through.

I have an idea on why scrubbing may not work:

The filesystem is mounted read only and on checksum errors on one disk scrub 
would try to repair it with the good copy from another disk.

Yes, this is it:

    merkaba:~>  btrfs scrub start -r /dev/satafp1/daten
    scrub started on /dev/satafp1/daten, fsid […] (pid=9375)
    merkaba:~>  btrfs scrub status /dev/satafp1/daten 
    scrub status for […]
            scrub started at Wed Nov 16 12:13:27 2016, running for 00:00:10
            total bytes scrubbed: 45.53MiB with 0 errors

It would be helpful to receive a proper error message on this one.

Okay, seems today I learned quite something about BTRFS.

Thanks,

-- 
Martin Steigerwald  | Trainer

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