It doesn't take a monster storm to lose everything, just a simple hard drive crash. Back up options range from simple to professional grade. None are terribly expensive and many are so well designed—like this Toby Wong inspired gold number from La Cie (above)—having an extra box around is no great hardship. Small, rugged portable drives will do the trick for many but files need to be manually saved. Automatic back up like Apple's Time Capsule let you schedule daily or hourly file saves but for extra protection try something used by professional photographers.
RAID mirroring, is basically multiple hard drives in one unit. Something like Western Digital's My Book Mirror Edition saves your data twice. Each drive mirroring the other, providing back up for your back up. And storage costs have fallen, making a terabyte of space available for about $289.