Backup without erasing?

[absinthe]

Originally Posted by dnanian

There's no reason to erase the backup drive every time you want to backup your user files. In fact, there's no reason for most users to back up the user files separately. Just use "Backup - all files" with Smart Update. It won't erase the whole drive, it'll just update the things that are changed, user files, system files, whatever. It's not slow...

Just to be clear, your advised procedure above must be applied to a backup drive that has been erased and copied via SuperDuper in the first place... right? In other words, I still need to run SD the first time on a backup drive that contains no other important files, or I will lose them in the initial backup process... correct?

Or can I leave important files on a backup drive, AND initiate a new SD backup procedure with no worries?