When running
rsync -Paz /home/sbird "/run/media/sbird/My Passport/sbird"
As told by someone, I run into a ran out of storage error midway. Why is this? My disk usage is about 385 GiB for my home folder, and there is at least 800 GiB of space in the external SSD (which already has stuff like photos and documents). Does rsync make doubly copies of it or something? That would be kind of silly. Or is it some other issue?
Note that the SSD is from a reputable brand (Western Digital) so it is unlikely that it is reporting a fake amount of storage.
A second possibility is the deduplication feature of BTRFS. If you made copies of files on your SSD, they only take up space there when changing something - thats how i keep 5 differently modded Cyberpunk 2077 installations on my drive while only taking up a fraction of space that would be needed - I wouldn’t be able to copy this drive 1:1 onto a different filesystem.
Ah, I knew the mention of btrfs heebied my jeebies a little, but forgot about the CoW thing.