2.5. Backing Up Your Database
You need to have at least one backup copy of your valuable database. Disasters occur rarely, but they do occur. The computer where your database is stored can break down and lose your data, the computer file can become corrupted, the building can burn down, and so on. Backup copies of your database guard against data loss from such disasters.
You should have at least one backup copy of your database stored in a location that's separate from the copy you currently use. You should probably have more than one copy — perhaps as many as three. Here's how you can store your copies:
Store one copy in a handy location, perhaps even on the same computer on which you store your database, to quickly replace a working database that becomes damaged.
Store a second copy on another computer in case the computer on which you have your database breaks down, making the first backup copy unavailable.
Store a third copy in a different physical location to prepare for the remote chance that the building burns down. If you store the second backup copy on a computer at another physical location, you don't need this third copy.