Re: Fixing a degraded RAID

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

Michael Welsh Duggan <mwd@md5i.com> writes:

> I had a disk in my RAID0 die:

My mistake.  This was a stupid typo.  The drives were in a RAID 1
configuration.  Both data and metadata are DUP'd.

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

>   root@maru2:~# /usr/local/src/btrfs-progs/btrfs fi show 8c530f6f-7592-4d57-854d-1fae33ae7cb6
>   Label: none  uuid: 8c530f6f-7592-4d57-854d-1fae33ae7cb6
>           Total devices 3 FS bytes used 329.66GiB
>           devid    1 size 1.79TiB used 357.03GiB path /dev/sdd1
>           devid    3 size 931.51GiB used 178.00GiB path /dev/sdf
>           *** Some devices missing
>   
>   Btrfs v3.12-43-gc2081e2-dirty
>
> So, I try to mount it with -o degraded.  That fails, implying that a
> degraded mount needs to be read-only.  So I successfully mount it read
> only.  Then I want to add a new disk to replace the missing one:
>
>   root@maru2:~# /usr/local/src/btrfs-progs/btrfs dev add /dev/sdg /mnt/
>   ERROR: error adding the device '/dev/sdg' - Read-only file system
>
> So I can't add a disk if it's mounted read-only, and can't mount it
> read-write?  What am I missing?  What's my way around this?

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