Raid5/BTRFS recovered/claimed almost 900 Gb of freespace by itself !!!

Hi guys,

I don't know what exactly happened, but OMV just went from 3600+ Gb to 4500+ Gb of free space. All my media files still seem to be there.

Well, the only think I might have done if to run a command line to get movie resolution so I can figure out which ones I can upgrade from 720p to 1080p for example.

find /sharedfolders/media/Movies/ -type f -exec bash -c 'sm=$(mediainfo "{}" | grep Width); echo $sm - "{}"' \;

The command is not supposed to delete anything, maybe it justed forced the system to sync some fs tables with the reality ?

After reading TFM, it looks like the "wasted" space was internally allocated by BTRFS, so before this magical thing happened, I was seeing the "unallocated" space (see at the very bottom) which was equal to free space I was initially seeing with the regular df command.

Now it's even more confusing, the free space calculated by df command is not the same as what's reported by btrfs.

Maybe there are some housekeeping operations on btrsf that get rid of allocated space that's no longer needed

Free space now:

root@openmediavault:~# df -h
Filesystem      Size  Used Avail Use% Mounted on
udev            7.6G     0  7.6G   0% /dev
...
/dev/md0         11T  6.6T  4.5T  60% /srv/dev-disk-by-label-DATA

root@openmediavault:~# btrfs fi usage /srv/dev-disk-by-label-DATA
Overall:
    Device size:                  10.92TiB
    Device allocated:              7.20TiB
    Device unallocated:            3.71TiB
    Device missing:                  0.00B
    Used:                          6.51TiB
    Free (estimated):              4.40TiB      (min: 2.54TiB)
    Data ratio:                       1.00
    Metadata ratio:                   2.00
    Global reserve:              512.00MiB      (used: 192.00KiB)


Data,single: Size:7.18TiB, Used:6.49TiB
   /dev/md0        7.18TiB


Metadata,DUP: Size:10.00GiB, Used:7.88GiB
   /dev/md0       20.00GiB


System,DUP: Size:8.00MiB, Used:944.00KiB
   /dev/md0       16.00MiB


Unallocated:
   /dev/md0        3.71TiB