Since you're not talking about dynamically changing data, but about static (albeit very large) files, I take issue with your original statement about there not being a simple backup strategy. There is. Get twice the storage you need, which you'd have to do for RAID Level 1 anyhow, and make copies of everything. If you don't want to buy another humongous disk drive, burn DVDs instead.

Depending on the kind of files these videos are, you might be able to save some space by compressing. It would probably take too long to decompress on a regular basis when you wanted to watch one, but for backup copies, why not? They're insurance, not for regular use. You probably won't ever need them.

It's not as sexy as RAID, but it's simpler and probably cheaper.