I’ve read a lot of the documentation regarding the transparent compression on BTRFS and what can it do, but I cannot accurately know how much actual space I am using on my disk. Using du -sh /home or df -h or btrfs filesystem df return the same result of ~33gb used, but when using compsize /home I get 23G of usage and 30G uncompressed in the TOTAL row.

So, what I don’t understand:

• What is the actual disk usage? Which tool is reporting the correct size?
• Will something happen if I get the uncompressed size to the size of my partition, but not the compressed size? Will the OS not let me write anymore despite having enough space?

Solved: if i mount the / btrfs subvol: sudo mkdir /mnt/nvmeroot && mount -o subvol=/ /dev/nvme0n1p15 /mnt/nvmeroot and use compsize /mnt/nvmeroot/ on it it reports the same size as the last commands and shows me the effectiveness of compression.