I use archlinux and manjaro. I recently bought an external 2TB toshiba stor.E canvio, and I planned to use it as back up. I used gpt layout and partitioned it with luks and ext4. Dolphin reports 6% full, whilst only 20kb are used. why is it so?I decided to use encrypted zfs/btrfs on it, but I don't know any of it's basis and jargon. what's the easiest way to do so.  
Encrypted file system on external storage
btrfs;zfs