1 root@archboot / # btrfs fi show; btrfs fi df /mnt/sdb3; uname -a                                             :(
failed to open /dev/sr0: No medium found
Label: none  uuid: 1b0fa67f-126f-4bf8-9f7a-01cca1fddc43
        Total devices 1 FS bytes used 15.77GB
        devid    1 size 17.24GB used 17.24GB path /dev/dm-1

Label: none  uuid: 92c42883-e8fa-472f-a47a-4db25bf48731
        Total devices 1 FS bytes used 11.02GB
        devid    1 size 19.53GB used 13.04GB path /dev/dm-0

Btrfs v0.20-rc1-358-g194aa4a
Data: total=14.46GB, used=14.46GB
System, DUP: total=8.00MB, used=16.00KB
System: total=4.00MB, used=0.00
Metadata, DUP: total=1.38GB, used=1.31GB
Metadata: total=8.00MB, used=0.00
Linux archboot 3.11.6-1-ARCH #1 SMP PREEMPT Sat Oct 19 00:29:46 CEST 2013 i686 GNU/Linux