Information Technology Reference
Store an Extra
No matter how many backups you have or how often you update them,
they do you no good if they disappear along with your computer—as
they likely will in the case of theft, fire, or any other serious disaster.
I urge everyone to take the precautionary step of keeping a second
copy of their backups safely away from their computer—preferably in
another building altogether. You can do this with a second hard drive—
or, more easily and economically, with an Internet backup service.
Use an Extra Hard Drive
If you purchase two or more hard drives, you can set each of them
up the same way; then, back up to one drive for a week, switch to the
other one, and take the first offsite. Repeat this rotation every week
or so, and you'll be safe in the knowledge that if you lose your first
backup, a second one is still available that's no more than a week out
Although you can use this process with just two drives, having three
is more convenient (although, of course, more expensive). At any time,
you'll have one drive (A) in use, your next-most-recent one (B) onsite,
and your oldest one (C) offsite. When you rotate the drives, you bring
your oldest one (C) back onsite and make it active, while taking what
has now become the oldest drive (B) offsite—and so on.
The safest way to keep multiple backup drives is to set them up
separately. Configure one drive with partitions for duplicate and
versioned backups. Set up Time Machine (or another versioned
backup program) and let it run; also create a bootable duplicate.
Then disconnect the drive and repeat the entire procedure with a
second drive. If you use Time Machine under Mountain Lion or later,
you can configure multiple destination drives, and Time Machine