My motto is that "you can never have too many backup tapes." Small business owners tend to backup onto one or two tapes and tell themselves that their data is safe. But backup tapes are prone to magnetic interference and wear out over the course of one year. I suggest that businesses have at least five backup tapes, though it's best to have ten or more. Label each tape with the day of the week. That way you'll have a valid backup in case of a catastrophe. Make sure you keep the four tapes that aren't in use away from the server -- in case the catastrophe is a leak.
If you're cautious enough to use ten or more tapes, label the first four Monday, Tuesday, Wednesday, and Thursday. Then, label the next five tapes Friday 1, Friday2, Friday3, Friday4, and Friday5. Use the Friday tapes only one Friday per month (Friday5 is for those few months that have five weeks). The last tape can be a spare that you use periodically and keep off-site. You'll have backups for at least a month's worth of data and feel much better when you hear that "The network is down."
