# sudo btrfs fi df /mnt/disk3
Data, single: total=12.70TiB, used=12.27TiB
System, DUP: total=8.00MiB, used=1.34MiB
Metadata, DUP: total=15.00GiB, used=14.50GiB
GlobalReserve, single: total=512.00MiB, used=608.00KiB

# mkdir /mnt/disk3/tst
mkdir: cannot create directory ‘tst’: No space left on device

I suspect this is BTRFS balancing issue, but even BTRFS’s own utility is indicating there’s still SOME space left. Certainly should be enough to create a directory.

Any ideas?

Just in general BTRFS default options for creating new volumes seem to not work well for disks that I intend to fill completely immediately after formatting. Are there better options for this use case? I just use

# mkfs.btrfs /dev/sdd1

  • jlsalvador@lemmy.ml
    10·
    7 months ago

    When you create a filesystem, there is a parameter named as “block percent free”. This parameter should be “5%”, so a 5% of your partition size can only be written by the “root” user.

    You can decrease this value or just free some space. You can try to create files or folders as root as well.

    • Hawke@lemmy.world
      4·
      7 months ago

      Is there any reason this 5% number still holds true? Back in the days of 40 MB hard drives it made sense to make sure the system didn’t totally run out while root was fixing the low disk situation … but these days even 1% is still several gigabytes of space, not likely to run out that quickly.

    • daq@lemmy.sdf.orgOP
      3·
      7 months ago

      Are you sure that’s the case with btrfs? I know ext has that feature. My understanding is btrfs just has a global reserve that can be used for any data in an low space situation.

      # sudo btrfs fi usage /mnt/disk3
Overall:
    Device size:                  12.73TiB
    Device allocated:             12.73TiB
    Device unallocated:            1.00MiB
    Device missing:                  0.00B
    Device slack:                    0.00B
    Used:                         12.29TiB
    Free (estimated):            449.43GiB      (min: 449.43GiB)
    Free (statfs, df):           449.43GiB
    Data ratio:                       1.00
    Metadata ratio:                   2.00
    Global reserve:              512.00MiB      (used: 0.00B)
    Multiple profiles:                  no

Data,single: Size:12.70TiB, Used:12.26TiB (96.55%)
   /dev/sdd1      12.70TiB

Metadata,DUP: Size:15.00GiB, Used:14.49GiB (96.58%)
   /dev/sdd1      30.00GiB

System,DUP: Size:8.00MiB, Used:1.34MiB (16.80%)
   /dev/sdd1      16.00MiB

Unallocated:
   /dev/sdd1       1.00MiB
  • wewbull@feddit.ukEnglish
    5·
    7 months ago

    For me the answer is always “snapshots” and normally because of docker.

    If you run a docker image store on a BTRFS drive, docker creates snapshots at various times. It never cleans them up; It has no commands that clean them up, and it means that if you delete a file it doesn’t free any space because the snapshots keep the file alive.

  • Possibly linux@lemmy.zipEnglish
    2·
    7 months ago

    As a rule of thumb you should keep your disk usage around 60% or under.

    My guess it that you have snapshots or other similar hidden data taking up space. List out your snapshots and sub volumes.

  • ffhein@lemmy.world
    1·
    7 months ago

    Would be nice if there’s some automatic solution, but after running into this issue I always run a couple different btrfs balance after deleting larger files for good measure. Took a while to figure out why Linux said there wasn’t any space left when df reported several GB available on the root partition

    • daq@lemmy.sdf.orgOP
      2·
      7 months ago

      I am surprised there isn’t an automatic mechanism to handle this especially if it is such a frequent issue.