root@shark:~# uname -a
Linux shark 3.14.3 #3 SMP Thu May 8 18:56:17 UTC 2014 x86_64 AMD Athlon(tm) 64 X2 Dual Core Processor 4600+ AuthenticAMD GNU/Linux

root@shark:/raid/music# btrfs fi df /mnt/btrfs/sharkpool/
Data, RAID0: total=2.41TiB, used=2.41TiB
System, RAID1: total=32.00MiB, used=160.00KiB
Metadata, RAID1: total=6.00GiB, used=4.93GiB
root@shark:/raid/music# btrfs fi sh
Label: none  uuid: e032e16a-7624-464f-815f-f92d6bd14f03
	Total devices 6 FS bytes used 2.41TiB
	devid    1 size 698.64GiB used 511.00GiB path /dev/sdb
	devid    2 size 931.51GiB used 517.03GiB path /dev/sdc
	devid    3 size 931.51GiB used 517.03GiB path /dev/sdd
	devid    4 size 465.76GiB used 464.76GiB path /dev/sde
	devid    5 size 465.76GiB used 464.76GiB path /dev/sdf
	devid    6 size 8.00GiB used 8.00GiB path /dev/loop0

Btrfs v3.14.2
root@shark:/raid/music# btrfs fi df /mnt/btrfs/sharkpool/
Data, RAID0: total=2.41TiB, used=2.41TiB
System, RAID1: total=32.00MiB, used=160.00KiB
Metadata, RAID1: total=6.00GiB, used=4.93GiB

root@shark:~# dmesg | tail
[3520978.250427] BTRFS info (device sdb): relocating block group 8670015389696 flags 9
[3521015.843117] BTRFS info (device sdb): found 123 extents
[3521020.453847] BTRFS info (device sdb): found 123 extents
[3521021.163228] BTRFS info (device sdb): relocating block group 8666794164224 flags 9
[3521058.820004] BTRFS info (device sdb): found 105 extents
[3521064.086513] BTRFS info (device sdb): found 105 extents
[3521064.895780] BTRFS info (device sdb): relocating block group 8245997469696 flags 9
[3521114.341161] BTRFS info (device sdb): found 717 extents
[3521122.642789] BTRFS info (device sdb): found 717 extents
[3521123.643947] BTRFS info (device sdb): 463 enospc errors during balance