Second raid is NOT a backup it's high availability.
That's entirely a matter of configuration. If I were doing this with drives, I'd grab an 8x SATA card, 8 4TB drives, an external hot-swap shelf, and setup RAIDZ-2 with compression on it. I'd put the drives in, rsync the data to them, snapshot it, pop them out, and bring them to a safe deposit box for safe keeping. Cost is about $1800. That's totally a backup. A second set of backups is another $1300.
Can somebody compare the cost for tape?
Also, stop hoarding stuff, it's expensive. My (legit) backups of my extensive DVD(2.4Mb/s h.264) and CD(FLAC) collection fits in less than 2TB.