# mkfs.btrfs -d raid6 -m raid1c3 -L DATA -f /dev/sda3 /dev/sdb3 /dev/sdc3 /dev/sdd3
btrfs-progs v5.4.1
See http://btrfs.wiki.kernel.org for more information.

Label:              DATA
UUID:               b0ae1908-2e56-441e-b733-613ac8bcdfea
Node size:          16384
Sector size:        4096
Filesystem size:    29.07TiB
Block group profiles:
  Data:             RAID6             2.00GiB
  Metadata:         RAID1C3           1.00GiB
  System:           RAID1C3           8.00MiB
SSD detected:       no
Incompat features:  extref, raid56, skinny-metadata, raid1c34
Checksum:           crc32c
Number of devices:  4
Devices:
   ID        SIZE  PATH
    1     7.27TiB  /dev/sda3
    2     7.27TiB  /dev/sdb3
    3     7.27TiB  /dev/sdc3
    4     7.27TiB  /dev/sdd3

# btrfs filesystem usage /home/
WARNING: RAID56 detected, not implemented
Overall:
    Device size:                  29.07TiB
    Device allocated:              6.02GiB
    Device unallocated:           29.06TiB
    Device missing:                  0.00B
    Used:                         63.80MiB
    Free (estimated):                0.00B      (min: 8.00EiB)
    Data ratio:                       0.00
    Metadata ratio:                   3.00
    Global reserve:               18.52MiB      (used: 16.00KiB)

Data,RAID6: Size:18.00GiB, Used:14.93GiB (82.94%)
   /dev/sda3       9.00GiB
   /dev/sdb3       9.00GiB
   /dev/sdc3       9.00GiB
   /dev/sdd3       9.00GiB

Metadata,RAID1C3: Size:2.00GiB, Used:21.25MiB (1.04%)
   /dev/sda3       1.00GiB
   /dev/sdb3       1.00GiB
   /dev/sdc3       2.00GiB
   /dev/sdd3       2.00GiB

System,RAID1C3: Size:8.00MiB, Used:16.00KiB (0.20%)
   /dev/sdb3       8.00MiB
   /dev/sdc3       8.00MiB
   /dev/sdd3       8.00MiB

Unallocated:
   /dev/sda3       7.26TiB
   /dev/sdb3       7.26TiB
   /dev/sdc3       7.26TiB
   /dev/sdd3       7.26TiB