SSH to instance with flyctl console:
# df -h
Filesystem Size Used Avail Use% Mounted on
devtmpfs 2.0G 0 2.0G 0% /dev
/dev/vdb 7.9G 1.3G 6.2G 17% /
shm 2.0G 0 2.0G 0% /dev/shm
tmpfs 2.0G 0 2.0G 0% /sys/fs/cgroup
/dev/vdc 988M 288M 634M 32% /app/apps/redacted/authData
# du -sh authData
286M authData
# touch authData/XXX
touch: cannot touch 'authData/XXX': No space left on device
#
Volume has 1GB and is mounted as /dev/vdc, it says it has 32% of space used but app is failing to write to it.