# btrfs fi show
failed to open /dev/sr0: No medium found
Label: none  uuid: c97a9cbb-0897-45e7-a8c8-94912b56a247
        Total devices 1 FS bytes used 2.66TB
        devid    1 size 2.96TB used 2.96TB path /dev/dm-16

Btrfs v0.20-rc1-333-gf392a28

# btrfs fi df /backup/bu002/vol04
Data: total=2.84TB, used=2.60TB
System, DUP: total=8.00MB, used=352.00KB
System: total=4.00MB, used=0.00
Metadata, DUP: total=61.00GB, used=60.88GB
Metadata: total=8.00MB, used=0.00

# mount | grep /backup/bu002/vol04
/dev/mapper/bu002-vol04 on /backup/bu002/vol04 type btrfs (rw,noatime,nodiratime,nospace_cache,noacl,compress-force)

# df /backup/bu002/vol04
Filesystem               1K-blocks       Used Available Use% Mounted on
/dev/mapper/bu002-vol04 3174252544 2922705572 251268060  93% /backup/bu002/vol04

# :>/backup/bu002/vol04/hello
/backup/bu002/vol04/hello: No space left on device.