I have a BTRFS Raid 1, with the following
btrfs fi show:
Total devices 4 FS bytes used 1.45TiB devid 7 size 698.64GiB used 694.15GiB path /dev/bcache32 devid 9 size 931.51GiB used 928.51GiB path /dev/bcache0 devid 10 size 698.64GiB used 694.64GiB path /dev/bcache48 devid 11 size 1.82TiB used 697.00GiB path /dev/bcache16
From here, you can see that the three smaller devices are almost full (in fact, they were completely full just a while ago, giving me
ENOSPC errors). However, the larger 2TB HDD is mostly empty.
The volume is "full" because any data added to the 2 TB disk must also be mirrored on the other disks, but they're all full. Ideally, I'd be able to move copies from the smaller disks to the 2 TB disk so I'd have room to add more data later.
btrfs balance seems to juggle the data around but doesn't actually make significant changes to the allocation proportions.
How can I fix this?