While checking for used and free space in a btrfs subvolume, I’m not getting a consistent value. It’s confusing and doesn’t help.
- What is the correct way to find used/free space?
- Why are these values inconsistent (except normal du)?
According to btrfs fi usage /home, 83.21 GiB is used.
Overall:
Device size: 149.98GiB
Device allocated: 100.07GiB
Device unallocated: 49.91GiB
Device missing: 0.00B
Device slack: 0.00B
Used: 83.21GiB
Free (estimated): 63.06GiB (min: 38.10GiB)
Free (statfs, df): 63.06GiB
Data ratio: 1.00
Metadata ratio: 2.00
...
As per btrfs fi df /home, used space is 82.86 GiB, not 83.21 GiB.
Data, single: total=96.01GiB, used=82.86GiB
System, DUP: total=32.00MiB, used=16.00KiB
Metadata, DUP: total=2.00GiB, used=178.61MiB
GlobalReserve, single: total=99.50MiB, used=0.00B
As per btrfs fi du -s /home , used space is 63.11 GiB.
Total Exclusive Set shared Filename
63.11GiB 13.64GiB 49.01GiB /home
While according to du -hs /home, 64GiB is used.
Also, maximum space used should be close to 72 GiB as per btrfs fi du -s / and 73 GiB as per du -hs /, if btrfs fi usage includes all subvolumes . ‘/home’ and ‘/’ are on separate subvolumes.
Between btrfs filesystem usage / and btrfs filesystem du -s / there’s nearly 11GiB difference for used space. I have checked btrfs du -hs <path/to/subvolume> for all subvolume in the filesystem, and total seems to be 72 GiB, hence the confusion. Still I don’t know if I’m using the tools properly or something else is at fault here.
To correct myself, 11GiB is additional space used by snapshot probably used space difference between . So btrfs fi usage and btrfs fi du -s / is because of diff between snapshot and parent volume (didn’t consider that while adding all used GiB of subvolumes)btrfs filesystem usage works well to check used/free space.
edit: fix incorrect args; additional space is not diff
