Even with the most reliable computer hardware and software, there is always the possibility that something can go wrong. Recovering from a disaster, such as a total disk crash or theft of a PC, can a be very traumatic event. This is true even when a backup exists; but when there is no backup, the situation is much, much worse. Fixing the problem can be an expensive process, although more costly is the time required. No matter how well you treat your system, no matter how much care you take, you cannot guarantee that your data will be safe if it exists in only one place.