Disk mirroring is the process of setting up a computer so that all the data is being written to multiple disks at the same time. This is generally done primarily for safety reasons because there is always a danger of hard-drive failure. Usually, disk mirroring involves two actual disks in the system, with one being the primary disk and the other being a backup. In some cases, people set up disk mirroring over long distances using powerful Internet connections.
Hard disk drives are considered fairly reliable most of the time, but they contain moving parts, and there is a general certainty that they will eventually fail with continued use. Many people protect themselves from this by doing a lot of data backups, but for some people, this isn’t safe enough. In these cases, disk mirroring ensures that there is always another perfect replica of the main system drive available.
Most individuals and companies that used disk mirroring do so because they are afraid of losing important data. Many individuals don’t bother with two hard drives for any reason, and for some people, the only worthy reason for having two hard drives would be for the increased storage space. People who decide to set up mirroring may have important jobs involving their computers, and they may fear that any data loss could be extremely detrimental their life or profession. When companies set up their computers with disk mirroring, it is often for the same kinds of reasons.
Many computers that are set up with disk mirroring use an arrangement called a redundant array of independent disks (RAID). This is a method of setting up multiple hard drives so that they can work together. There are several versions of RAID and they are generally numbered RAID 0, RAID 1, etc. RAID 0 is a way of using two hard drives for increased performance, and RAID1 is used for mirroring.
Another way of setting up disk mirroring is to have another hard drive at another location that is constantly being updated with data through an online connection. Sometimes this approach isn’t entirely in real time, but it is usually very close if possible. The idea for this kind of setup is to have a replacement hard drive available in case some kind of disaster happens, such as a fire. This kind of approach might be used by major government institutions, people involved in scientific research, or anybody else that has an absolutely vital need to protect his data at all costs.