> We can check that there are, in fact, no unexpected subvolumes. > > btrfs sub list / > > In particular, I wonder if you have subvolumes/snapshots hidden behind > the mounted subvolume. > > Also, I don't think it's really the case here with only 16GB reported by > du,, but do you have any large, heavily fragmented files, such as VM > virtual disks? Without defragmentation or compression, I've seen those > consume more than twice their reported file size on btrfs.
thanks for the hint! i have only considered snapshots but no subvolumes. since them considered as file system boundary and i had set the option -x, --one-file-system, it is clear where I waste my storage space. my fault - thank you!
