I have an existing BTRFS drive (/dev/sde), I added a new drive to the system, mounted it and formatted as BTRFS in gparted and then I get:

sudo btrfs fi show

Label: none  uuid: f54ed81a-2d6a-4cf7-88d3-b8538c2b27c6
    Total devices 1 FS bytes used 512.00KiB
    devid    1 size 5.46TiB used 2.06GiB path /dev/sdd1

Label: none  uuid: 01dba537-b5c4-44f6-b198-a03972c4196f
    Total devices 1 FS bytes used 1.69TiB
    devid    1 size 3.64TiB used 1.71TiB path /dev/sde


sudo btrfs filesystem df /mnt/local/int001


Data, single: total=1.70TiB, used=1.68TiB
System, DUP: total=8.00MiB, used=208.00KiB
System, single: total=4.00MiB, used=0.00B
Metadata, DUP: total=3.00GiB, used=2.11GiB
Metadata, single: total=8.00MiB, used=0.00B
GlobalReserve, single: total=512.00MiB, used=0.00B

I want to convert this to RAID 1, is there any issue with what you see here, should I be able to do a conversion to raid now and how would I do it?

I've tried:

sudo btrfs balance start -dconvert=raid1 -mconvert=raid1 /mnt/local/int002
ERROR: error during balancing '/mnt/local/int002' - Invalid argument

There may be more info in syslog - try dmesg | tail

1 Answer 1


The mistake you made is that you created two separate BTRFS filesystems. You can see in the output of sudo btrfs fi the two filesystems, each with one device.

To fix it, use the btrfs device add command to add the new disk to the existing filesystem. THEN do the rebalance.


  • I did wonder if that was the case, I'll try to 'add' a little later and report back, thnx. Jul 5, 2017 at 13:35

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