Atemu , 3 months ago

As per btrfs fi df /home, used space is 82.86 GiB, not 83.21 GiB.

That’s just used data. The global used metric likely incorporates metadata etc. too. System aswell as the GlobalReserve are probably accounted as fully used as they’re, well, reserved.

As per btrfs fi du -s /home , used space is 63.11 GiB.

<span style="color:#323232;">     Total   Exclusive  Set shared  Filename
</span><span style="color:#323232;">  63.11GiB    13.64GiB    49.01GiB  /home
</span>

While according to du -hs /home, 64GiB is used.

Likely compression or inline extents. btrfs only reports apparent size to du and friends unfortunately.

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.

Your home has a lot of shared extents which indicates to me that you have at least one snapshot of it.

You also wrote 13.6GiB of new data to your home since the snapshot. Assuming a similar amount of data was deleted/overwritten since, that would add up to 76GiB. If there’s perhaps one or two more snapshots, that would explain the rest.

Snapshots are “free” only so long as you don’t write or delete any data in the origin.