Hey, I'd recommend taking a look at Syncthing. It's software that runs locally, and you can configure the synchronisation to occur in a unidirectional flow instead of bidirectional. I.e. configure it to only synchronise data from the source drive to the backup drive.
Hope this helps and all the best!
EDIT: As pointed out, Syncthing is more suited to syncing data between two or more devices so may not be the right solution for OPs use case.
Hey, these days I defer to TheMovieDB instead of IMDB. They don't develop their own app, however there are 3rd party apps using their API, a list of which can be found here.
Source
Hope this helps and all the best!