RAID configurations are great additions to a network server because they can add speed and redundancy depending on which setup you have. So what is redundancy and how is it achieved in a RAID?
Redundancy means that your system contains duplicate copies of a file. In the event of a failure you have another available copy to work with which is great if you can't afford to lose any of your files. Redundancy is achieved by "striping", "mirroring" or a mix of "striping and parity".
RAID 0 is the only RAID configuration that does not provide redundancy, it provides a speed boost but if a drive fails you're out of luck.
RAID 1 achieves redundancy by having identical copies of a disk which is known as data mirroring.
RAID 2 uses data striping with error correcting code to achieve redundancy.
RAID 3 uses parity information to achieve redundancy.
RAID 5 matches striping and parity to achieve data redundancy.
RAID 6 uses striping and double parity across drives to achieve redundancy.