Re: Fixing a degraded RAID

[Michael Welsh Duggan <mwd@md5i.com>]

Xavier Bassery <xavier@bartica.org> writes:

> On Fri, 18 Apr 2014 23:23:56 -0400
> Michael Welsh Duggan <mwd@md5i.com> wrote:
>
>> Michael Welsh Duggan <mwd@md5i.com> writes:
>> 
>> root@maru2:~# /usr/local/src/btrfs-progs/btrfs fi df /mnt/
>> Data, RAID1: total=353.00GiB, used=328.24GiB
>> System, single: total=32.00MiB, used=56.00KiB
>> Metadata, RAID1: total=4.00GiB, used=1.43GiB
>
> As Chris Murphy noted, your "System" chunk still reported as "single"
> is likely the issue here.  This reminds me of a bug i stumbled upon
> once: https://bugzilla.kernel.org/show_bug.cgi?id=60594
>
> Have you converted your fs from SINGLE to RAID-1 profile by running a
> balance?

Yes, I did.  And I think I was still on 3.10 or 11 when this happened.

> This conversion bug should no longer occur with the patch "Btrfs: stop
> refusing the relocation of chunk 0" which has been merged since 3.12.
> But chances are that you've converted your fs with an older kernel
> without that patch.  While Ilya Dryomov investigated the issue on my
> system, we managed to work around this by using a patched module that
> ignored the safety measure refusing to mount rw in this case.
>
> I still have the patch, but i think the safest way and only other
> option would be to copy the data from your ro fs and recreate it from
> scratch.  Doing so with recent btrfs progs (v3.12 or newer) you'll
> benefit from the new default metadata blocksize of 16KB that should
> increase performance.

Right.  *sigh*  A pain, but needs must, and all that.  Thanks for your
help.

-- 
Michael Welsh Duggan
(md5i@md5i.com)