# 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
Looking at balancing might be right place to start. ref, https://archive.kernel.org/oldwiki/btrfs.wiki.kernel.org/index.php/FAQ.html#Help.21_I_ran_out_of_disk_space.21
You might want to start by rebalancing by percentages and not all at once. If nothing else it’ll tell you much sooner if you’re on the right track or not. Something like
sudo btrfs balance start -dusage=20 -musage=20 /mnt/disk3to work on only blocks that are 20% full or less. That should coaleace them into single data blocks and free up some others.