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.
WDYM by “diff”?
Also forgot to mention but if you want to know what’s taking how much space on your btrfs, try
btdu. It uses a sampling-based approach and will therefore never be 100% accurate but it should be quite accurate enough after a little bit.just comparing the subvolume with its snapshot with
btrfs send -p /example/subvol /snapshot/of/example/subvol >examplediff.btrfs.From
man btrfs-sendThanks for btdu, it seems useful as ‘btrfs fi du’ probably doesn’t account for compression, will check it out sometime.
Note that the diff does not necessarily correlate with the amount of data that changed, not how much additional space the snapshot takes.