Hey there, @Tylor Schuessele!
Unfortunately, I'm afraid that this setup is not really what you are looking for. If you want to backup your old photos and videos, I'd advise you have multiple duplicates of these media files stored in different locations on-site as well as off-site. RAID 1 is not a backup solution, if you don't have a duplicate of the files stored on the RAID 1 somewhere off-site (externally) as well!
Another reason why this won't work is the fact that the 8 TB HDD will be limited to the capacity and capabilities of the 2 TB HDD. This means that you will be able to use only 2 TB out of those 8 TB which definitely not an optimal storage setup. You cannot RAID 1 two different drives without consequences, that's why it's...