Help with space

Justin Brown
2014-02-27T18:19:06Z

I've a 18 tera hardware raid 5 (areca ARC-1170 w/ 8 3 gig drives) in
need of help. Disk usage (du) shows 13 tera allocated yet strangely
enough df shows approx. 780 gigs are free. It seems, somehow, btrfs
has eaten roughly 4 tera internally. I've run a scrub and a balance
usage=5 with no success, in fact I lost about 20 gigs after the
balance attempt. Some numbers:

terra:/var/lib/nobody/fs/ubfterra # uname -a
Linux terra 3.12.4-2.44-desktop #1 SMP PREEMPT Mon Dec 9 03:14:51 CST
2013 i686 i686 i386 GNU/Linux

terra:/var/lib/nobody/fs/ubfterra # parted -l
Model: Areca ARC-1170-VOL#00 (scsi)
Disk /dev/sdb: 21.0TB
Sector size (logical/physical): 4096B/4096B
Partition Table: gpt

Number Start End Size File system Name Flags
1 1049kB 21.0TB 21.0TB Linux filesystem

terra:/var/lib/nobody/fs/ubfterra # du -shc *
1.7M 40588-4-1376856876.jpg
2.7M 40588-4-1376856876b.jpg
1008G Anime
180G Doctor Who (classic)
5.5T Downloads
28G Flash Rescue
1.9T Jus
3.6T Tornado
4.0K dirsanime
4.0K filesanime
55G home videos
0 testsub
4.0K unsharedanime
13T total

terra:/var/lib/nobody/fs/ubfterra # btrfs fi show /dev/sdb1
Label: ubfterra uuid: 40f0f692-c68c-4af7-ade2-c15a127ceab5
Total devices 1 FS bytes used 17.61TiB
devid 1 size 19.10TiB used 18.34TiB path /dev/sdb1

Btrfs v3.12

terra:/var/lib/nobody/fs/ubfterra # btrfs fi df .
Data, single: total=17.58TiB, used=17.57TiB
System, DUP: total=8.00MiB, used=1.93MiB
System, single: total=4.00MiB, used=0.00
Metadata, DUP: total=392.00GiB, used=33.50GiB
Metadata, single: total=8.00MiB, used=0.00

I use no subvolumes nor are there any snapshots, at least as near as I
can tell. Any suggestions as to how to recover the missing space
assuming it's possible? Any help is most appreciated.

-Justin