As Mark says the tapes are really the best backups as long as you keep them carefully
It would be uneconomical to store them on HDD given how much they would gobble up in space.
Even edited DV AVI files can be rerecorded to tape for archiving
DVDs can also be fickle unless you get good media, burn them at nice low speeds handle and store them very very carefully
Incidentally I store some "precious" DVDs as ISO images on HDD which i treat like the "Crown Jewels"

HDD is cheap at about £70 for 320Gb but tapes are still way ahead as VFM in the archiving dept