Initial Backup Archive

I plan to use rdiff-backup on Windows using Windows networking - e.g. drive
letter for remote file access. I have a mirrored copy of files already on
the backup system.

1) Can I run rdiff-backup for the first time with a pre-populated backup
directory?

2) Do I need to set any options or configuration to make sure rdiff-backup
correctly processes this populated backup directory so that subsequent
changes will be archived, etc.?

Thanks much!