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I have the following RAID1 btrfs set:

Label: none  uuid: 87595481-7b5c-464e-b10d-d9b2b0852e11
        Total devices 4 FS bytes used 4.77TiB
        devid    1 size 2.73TiB used 2.63TiB path /dev/sdb
        devid    2 size 2.73TiB used 2.63TiB path /dev/sdc
        devid    3 size 2.73TiB used 2.63TiB path /dev/sdd
        devid    4 size 2.73TiB used 2.63TiB path /dev/sde

Btrfs v3.12

However I now have a robust backup solution and would like to get some of that RAID space back and just go JBOD as the data is reproducible and for this box I care more about capacity than reliability.

According to the btrfs wiki moving up to RAID1 from a JBOD setup is quite straightforward: btrfs fi balance start -dconvert=raid1 /mnt

Is it as simple as btrfs fi balance start -dconvert=single /mnt? What about the metadata? It's probably a good idea to leave that in RAID1 I assume?

Preparatory steps made:

  • Backups complete
  • 14.04 trusty with wily backported 4.2.0 kernel

1 Answer 1

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I think you nailed it with;

btrfs balance start -dconvert=single /mnt

The system should start to work hard moving around the data into JBOD. Yes, metadata will still be raid1 (at least if you configured it that way, which I'm assuming). You could change that too if you want to live more dangerously with -mconvert tacked on.

Confirm the success showing raid levels of data and metadata with;

btrfs fi show

And your new storage utilization numbers with;

btrfs fi df /mnt

Though, as you said, you have a good backup worked out so don't care about redundancy why not raid0? All the disks are the same size anyway. JBOD gives you flexibility to mix sizes down the road I guess...

See this response for more information.

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