This is really helpful thank you! I think it’s samba share? Whatever Unraid has just baked in and calls “shares”.

Googling rsync that looks like it’ll work, and faster is better!

While I do want true backups of a few drives (as in: if a drive fails, restore the backup to a new drive, physically swap it out, and you’re good to go), the majority of the data I’m just looking to have it “backed up” (as in: all of the files are present in more than one location). The majority of the data is ~18TB of media for my plex server. My unraid is: 1x 2TB, 1x 10TB, 1x20TB and 1x20TB(parity). It sounds like Rsync-ing the 20TB drive with my plex media and the 20TB unraid disk would get me what I need?

Thanks for the pointers, getting a few things to google is incredibly helpful.