JW77, as long as your raid backups are not in the same array as your media, meaning either offiste or on prem in another setup that runs a backup nightly of all your machines at 3am. There are tons of great FOSS backup solutions, find the one that best suits your needs (I use Rsync currently). If it’s all in the same setup, I tend to live by the mantra that just using Raid alone in your setup is NOT a Backup. Here’s current list of good backup solutions:
For your unraid box, I would definitely go with Unraid for your usecase.
As a rule of thumb you can stay with one parity disk (RAID5) with up to four data disks, and then using one parity disk for each group of seven data disks, like in the table:
||2 - 4
||5 - 14
||15 - 21
||22 - 28
||29 - 35
||36 - 42
I really hope this was helpful!
Cheers Live Pono