Quote:
Originally Posted by lazjen
That's why you buy 2. 
Or, on some systems, there's ways of combining diskspace over multiple disks to give a greater virtual drive size. |
To follow up from Chris,
Windows, Linux, Mac OS X all support RAID arrays.
RAID stands for Redundant Array of Inexpensive Disks.
What is termed a RAID 1 array is where you get two drives that provide
a mirrored set. The same data is written to both, providing redundancy.
If one drive fails, the system keeps running.
There are other levels of RAID that either provide for spanning of data
over two more more disks or for spanning with data with back up
redundancy should a disk fail in the set.
Redundancy through RAID arrays can in some situations circumvent the
need for a dedicated backup or perhaps increase the time period between
backup snapshots.
Most mission critical systems use some form of RAID storage.
In data centres the disks are often "hot swappable".
It's usually easy to set up RAID with commodity disks such as these
on a home computer. Google for your favourite OS.