In
Jim Slager said:
Joe, I don't understand why every PC model doesn't have an option to
have two identical drives installed at the factory with them actually
as mirrors so that every write goes to both and reads come from the
primary drive. If the primary fails then the system automatically
switches over to the secondary and leaves a message that the owner
should replace the bad disk. This way the user wouldn't even have to
fool around with backups since it would be done automatically. The
price of the second disk is not very high nowadays.
Disk mirroring is a technique used in a situation where a high
degree of uptime is required. It permits the system to stay up if
the primary drive fails, by automatically switching to the
mirror.
However it is *not* at all a good substitute for a backup. It
protects you against a single occurence--failure of the hard
drive--but leaves you vulnerable to all the other common problems
that backups should be used for. These problems include severe
power glitches, lightning strikes, virus attacks, accidental
deletion of needed files, theft of the computer, etc.
Everybody uses his computer differently, and has different
amounts of pain if data is lost. Each person's backup scheme
should reflect that need. But if your data is important enough,
secure backup needs to be on removable media; this protects you
against events like those mentioned above. For *really* secure
backup (for example if the life of your business depends on the
data), there should be multiple generations of backup and at
least one of those generations should be stored off-site.