$ sudo btrfs fi show
Label: none  uuid: 7b7c1694-ab10-4bed-a22e-544c8875f9f5
        Total devices 1 FS bytes used 105.43GiB
        devid    1 size 465.66GiB used 134.04GiB path /dev/sda2

Label: none  uuid: f0d4f203-f70d-4a84-b18d-a1f34ffdaa8b
        Total devices 1 FS bytes used 375.39GiB
        devid    1 size 465.66GiB used 458.04GiB path /dev/sda4

Label: none  uuid: 8de0ca54-5828-4c4a-9677-f17e02d852ae
        Total devices 2 FS bytes used 11.75GiB
        devid    1 size 465.66GiB used 463.66GiB path /dev/sda3
        devid    2 size 4.00GiB used 4.00GiB path /dev/loop0

Label: 'web'  uuid: 7e0998f9-e5c1-44cd-a64a-3a58cc695633
        Total devices 1 FS bytes used 14.95GiB
        devid    1 size 600.00GiB used 19.04GiB path /dev/sdb3

Label: 'postgres'  uuid: f74a76c9-7818-4de7-91f6-32067fdf52e4
        Total devices 1 FS bytes used 557.81GiB
        devid    1 size 1.00TiB used 563.04GiB path /dev/sdb4

Label: 'tests'  uuid: b7dfbb14-8ed0-4d2a-9a77-082a04c4ce0f
        Total devices 1 FS bytes used 880.14GiB
        devid    1 size 2.09TiB used 937.04GiB path /dev/sda6

Label: 'mysql'  uuid: 79d0464c-0c89-4eee-b970-dc222d095dd6
        Total devices 1 FS bytes used 681.88GiB
        devid    1 size 1.00TiB used 722.00GiB path /dev/sdb2

Label: 'video'  uuid: 95322683-9183-475d-aa4d-9ac3775d3972
        Total devices 1 FS bytes used 1.84TiB
        devid    1 size 2.00TiB used 2.00TiB path /dev/sda5

Label: 'mongo'  uuid: fb79f4b3-02ea-465e-8cbc-e4c3fc503e92
        Total devices 1 FS bytes used 465.03GiB
        devid    1 size 891.93GiB used 468.04GiB path /dev/sdb5

Label: 'video'  uuid: 827e5715-e265-4c88-92cd-57d592ba6d14
        Total devices 1 FS bytes used 384.00KiB
        devid    1 size 2.00TiB used 2.04GiB path /dev/sdb1

Btrfs v3.17
$ sudo btrfs fi df /var
Data, single: total=453.63GiB, used=11.58GiB
System, DUP: total=8.00MiB, used=96.00KiB
System, single: total=4.00MiB, used=0.00B
Metadata, RAID1: total=4.00GiB, used=144.34MiB
Metadata, DUP: total=3.00GiB, used=26.64MiB
Metadata, single: total=8.00MiB, used=0.00B
GlobalReserve, single: total=120.62MiB, used=0.00B