Not sure, what you mean by "takes the snapshot from zero".
Do you have different subvolumes defined (and mounted) in your BTRFS filesystem for / and /home (plus maybe some more)?
Creating a ro snapshot of a subvolume should be instant. Only if you want to send/receive it somewhere else, should it take time (depending upon the amount of data to be transferred).
I meant that it doesn't simply take an existing snapshot and "updates" it, which is a relatively quick process. It does a full scan, like when you do it for the first time, which takes a very long time.
I think it's a permissions problem actually. Don't worry, I'll figure it out! Thanks
As I wrote, when you _create_ (take) a snapshot of your btrfs subvolume (which could be mounted to "/" for example) it's quite literally "instant". Only when you want copy/send this snapshot to another filesystem or disk it will take some time, even if you copy/send incrementally, so only the blocks changed since the reference snapshot.
Maybe you're not using a reference snapshot at all? In which case all data (not only the modified blocks) in the current snapshot would have to be transferred.
In any case, happy tinkering 👍
