RAID (Redundant Array of Inexpensive Disks) is an emerging data storage technology which merges two or more physical hard disks into a single coherent unit by using either special hardware or software, in addition it also offers excellent read speed and a write-speed that is comparable to that of a single disk. Hardware solutions frequently are intended to present themselves to the attached system as a single hard drive, and thus the operating system unaware of the technical workings. Software solutions are distinctively implemented in the operating system, and in return would present the RAID drive as a single drive to applications.
Mirroring is one of the two data redundancy technique used in RAID for maintaining data consistency. In a RAID system using mirroring, for example (RAID I, suitable for data which reliability requirements are exceptionally high) writes two copies of the data, all data in the system is written simultaneously to two separate drives instead of one.This is also called fault tolerance because if one of the mirrored drives suffers a mechanical failure or does not respond, it should switch using the mirror drive with no lapse in user accessibility and the remaining drive will keep on functioning. The logic behind mirroring is to provide 100% data redundancy and full protection against the failure of either of the disks containing the duplicated one and let the data automatically directed to the other, thus mirroring setups constantly require a number of few drives and high technical skills to set-up for apparent reasons.
The key concept of mirroring is that it should provide not only complete redundancy of data, but also it should logically make fast recovery from a disk failure because all the data is on the second drive, it must ready to use if the first one fails. However while buying RAID make sure to buy twice the capacity considering if your requirement is extermlly high for data to which high performance access is required. .
