I converted my ext4 partition to btrfs and deleted the save subvolume after doing so. Then I enabled the compression (lzo) of the filessystem in the fstab file and everything is correct so far. Then I forced the compression of all files using the defragmentation command with the parameter -c that the new compression is applied to all files. While doing so, I noticed that my ssd got completly filled up - before I had 6gigs of free space. No I got nothing left. easteregg@x201s:~$ btrfs fi df / Data: total=50.00GB, used=49.17GB System: total=32.00MB, used=4.00KB Metadata: total=24.50GB, used=9.86GB and easteregg@x201s:~$ df -ha Filesystem Size Used Avail Use% Mounted on /dev/sda1 75G 60G 852M 99% / So now. How can I regain my free space. I expected to gain more space because of the lzo compression. And now! The fs is correctly mounted. easteregg@x201s:~$ mount /dev/sda1 on / type btrfs (rw,noatime,ssd,compress=lzo) Any ideas how to fix this issue?