>>107046991
>How do you know if you get 3 minutes or 30 until it finishes
Because it's your data on your storage, and you should have a rough idea how long it's going to take given the program just reads and compares all the files in both directories without calculating anything. It does print mismatches as soon as it finds them.

There are also myriad ways to check its progress externally. Not least modern terminals giving you visual alerts when your process exits.

Basically just stop losing your mind over trivial differences.