@anthony74700: RAID1 is an expensive way to just protect data in my opinion - I run RAID-Z2, which is effectivel RAID-6, i.e. two parity drives and multiple data drives. It depends on how valuable your data is, and how easily (if at all) you could replace it.
... which brings me to: RAID is not backup. Say it again, "RAID IS NOT BACKUP". And just in case, "le RAID n'est pas la suavegarde". If your data is that valuable, what happens if you drop your NAS? If it's stolen? If the house catches fire? If the children/dog/you are sick on it or drop a bottle of 1974 Chateauneuf onto it? RAID is a way of reducing downtime due to disc failure, but you should have a backup plan as well if it's worth doubling your discs for.
By the by, the WD box looks fine on paper - I always used to use Synology myself, which were great little boxes - you could also look to QNAP or a bit of a self-build with something like FreeNAS.
@joelbaby: an i5 NUC is probably overkill just to watch films and TV, unless you're also using it for gaming - in which case, you may need more GPU grunt than the on-board graphics can give. Maybe. 4Gb is plenty for 'buntu, a bit tight for WIndows. Otherwise, this would be an always-on(-sometimes) NAS if that's convenient. How well it works depends on you LAN connection and what you'd be sharing, but I can't see even HD videso really presenting a problem if your NUC were wired in - wireless would be a different matter. Same comments for backup as above, particularly for a USB drive that's more susceptible to physical (specifically, gravity-assisted) damage. Not sure where the "Seagate backup" figures here, though.
I understand Raid1 is not a backup solution, my bad for the vocabulary, but this is what I need.
