btrfs fi usage /mnt/nas

gistfile1.txt

 ❯ btrfs fi usage /mnt/nas
Overall:
    Device size:                  16.37TiB
    Device allocated:             11.67TiB
    Device unallocated:            4.71TiB
    Device missing:                  0.00B
    Used:                         11.19TiB
    Free (estimated):              2.50TiB      (min: 2.50TiB)
    Data ratio:                       2.00
    Metadata ratio:                   2.00
    Global reserve:              512.00MiB      (used: 0.00B)

Data,RAID1: Size:5.72TiB, Used:5.57TiB
   /dev/sdb        1.54TiB
   /dev/sdc        1.54TiB
   /dev/sdd        4.17TiB
   /dev/sde        4.17TiB

Metadata,RAID1: Size:120.00GiB, Used:23.75GiB
   /dev/sdb       10.00GiB
   /dev/sdc       10.00GiB
   /dev/sdd      110.00GiB
   /dev/sde      110.00GiB

System,RAID1: Size:32.00MiB, Used:960.00KiB
   /dev/sdd       32.00MiB
   /dev/sde       32.00MiB

Unallocated:
   /dev/sdb        1.18TiB
   /dev/sdc        1.18TiB
   /dev/sdd        1.18TiB
   /dev/sde        1.18TiB