Re: btrfs balance start -dconvert=raid5 on raid1 not converting to raid5

[Omar Sandoval <osandov@osandov.com>]

On Sat, Apr 25, 2015 at 04:47:31AM +0200, None None wrote:
> I tried to convert my btrfs from raid1 to raid5 but after the balance command it's still raid1.
> Also for raid56 the wiki says "Parity may be inconsistent after a crash (the "write hole")"
> does that mean if I convert metadata to raid5/6 and the parity becomes inconsistent my btrfs will be lost?
> 
> Kernel is v4.0 on debian/sid
> The filesystem was created with nodesize 8k if I remember correctly
> Mount options for /srv/ noatime,nodev,space_cache,subvol=@
> No snapshots and only a few subvolumes
> Free space is ~450GiB
> 
> To convert the data profile to raid5 (with btrfs-progs v3.17) I did
> btrfs balance start -v -dconvert=raid5 /srv/
> but after the the command was done (after 10 days)
> btrfs fi sho /srv/
> still shows data as raid1, free space is also what would be expected for raid1
> no errors, no problems, no raid5
> 
> 
> So I compiled the newer btrfs-progs v3.19.1 and did (I also tried raid6, same result still raid1)
> btrfs balance start -v -dconvert=raid5 -dlimit=1 /srv/
> Dumping filters: flags 0x1, state 0x0, force is off
>   DATA (flags 0x120): converting, target=128, soft is off, limit=1
> Done, had to relocate 1 out of 12071 chunks
> 
> dmesg shows only this, no errors
> [170427.207107] BTRFS info (device sdj): relocating block group 65294058848256 flags 17
> [170461.591056] BTRFS info (device sdj): found 129 extents
> [170476.270765] BTRFS info (device sdj): found 129 extents
> 
> btrfs fi sho /srv/
> shows all data as raid1
> 
> 
> btrfs fi sho
> Label: none  uuid: xxxxxxxx-xxxx-xxxx-xxxxxxxxxxxxxxxxx
>         Total devices 9 FS bytes used 11.78TiB
>         devid    1 size 2.73TiB used 2.62TiB path /dev/sdh
>         devid    2 size 2.73TiB used 2.62TiB path /dev/sdj
>         devid    3 size 2.73TiB used 2.62TiB path /dev/sdg
>         devid    4 size 2.73TiB used 2.62TiB path /dev/sdi
>         devid    5 size 2.73TiB used 2.62TiB path /dev/sdf
>         devid    6 size 2.73TiB used 2.62TiB path /dev/sde
>         devid    7 size 2.73TiB used 2.62TiB path /dev/sdc
>         devid    9 size 2.73TiB used 2.62TiB path /dev/sdd
>         devid   10 size 2.73TiB used 2.62TiB path /dev/sda
> 
> btrfs-progs v3.19.1
> 
> 
> btrfs fi df /srv/
> Data, RAID1: total=11.76TiB, used=11.76TiB
> System, RAID1: total=32.00MiB, used=1.62MiB
> Metadata, RAID1: total=17.06GiB, used=14.85GiB
> GlobalReserve, single: total=512.00MiB, used=0.00B
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This is a known bug in v4.0. I sent in a patch [1] to revert the commit
that caused the regression, but it didn't get any response. You could
apply that or just revert 2f0810880f08 ("btrfs: delete chunk allocation
attemp when setting block group ro") to fix your problem for now.

[1]: https://patchwork.kernel.org/patch/6238111/

-- 
Omar