I've long ago grown past the capacity of any available optical media, and while a tape drive could handle the sheer volume of data, anything large enough is well beyond my finances. I obsess over preserving my data. My last three computers have had RAID arrays, and even my laptop was ordered with mirrored hard drives, at considerable expense. I have multiple external hard drives that I back up to, including a network attached storage device so I can keep a copy of my data in another room and a pocket drive I could grab in the event of a natural disaster.
But none of that would help in the event of a fire or flood when I'm not home, and carrying around the pocket drive would risk data falling into the wrong hands. I could deal with losing my things, my computers, my books or my furniture; all these things are insured. But nothing could bring back lost data.
The other day I was surfing Amazon.com when I came across the SentrySafe Fire-Safe Waterproof Data Storage Chest. It has a USB pass-though; you place a 2-1/2" hard drive or flash drive inside, connect it to the internal USB port, close and seal the lid, then run a USB cable from the back of the safe to your computer. You can then access the drive without having to remove it from the safe. It can also protect CDs and DVDs, or anything else you can fit into a 5 inch cube.
It's a bit pricey, $146.50 from Amazon with free shipping, and it's fairly big (a cube about 10 inches per side), but this will really give me some peace of mind about my data. They also have larger versions with 1.2 cubic feet or 2 cubic feet of space, but they're $400 and $700, respectively. I already have a fire and water proof case for my non-electronic valuables, so I didn't need the larger units.