Redundant Array of Independent Disks, or RAID, is a method of saving content on a number of hard drives concurrently. A RAID can be software or hardware depending on the hard drives which are used - physical or logical ones, yet what is common between them is the fact that they all operate as a single unit where information is kept. The top advantage of employing a RAID is redundancy as the information on all of the drives shall be exactly the same all the time, so even if a drive fails for whatever reason, the information will still be available on the remaining drives. The overall performance is enhanced as well because the reading and writing processes could be split between different drives, so a single one will never be overloaded. There are different kinds of RAIDs where the efficiency and fault tolerance may differ based on the specific setup - whether information is written on all drives real-time or it's written on a single drive and afterwards mirrored on another, what amount of drives are used for the RAID, and so on.