As a trained advanced open water scuba diver, I understand all too well redundancy. On every shoot I have two duplicate camera bodies and a multitude of lenses that if need be can overlap because well after all it's technology.
While the camera shoots tethered to the computer saving the RAW file onto the computer's hard drive. The camera itself makes two copies of those files, one on each memory card. So when I leave a shoot, I already have three copies of each RAW file.
When I am back in the studio, I burn from the computers hard drive two copies on multiple DVD's. A typical day of shooting produces 8 gigabytes worth of files. Then I transfer those RAW files onto one of three, 3 terabyte hard drives (say that 10 times fast;).
Then after tagging the best RAW files from the group of exposures, I spend about 20 minutes on each file determining, color temperature, contrast, recovery along with a myriad of other decisions that gets me toward the next step. After going through the "keepers", I transfer them to another folder and burn another DVD. Then after spending another 15 or so minutes on the "keepers" I save them as Tiff's into a separate folder and burn another DVD of that set. This becomes the final set to distribute from and depending on their ultimate destination I will apply a final layer of post production sharpening.
So after each shoot, there are 4 DVD's that contain a version of each image, plus the files that are stored on the hard drives.
So in addition to the two hours I spend scouting each upcoming shoot, then of course the day of shooting itself, I typically spend another 4-5 hours in my studio, in front of the computer processing and saving along the way. See now you know why I wear such thick glasses;)
So while I may have lost some of you at 1 Megabyte, 2 Gigabyte, 3 Terabyte, I just thought you would want to know how safe your files are:)