Redundant Array of Independent Disks, or RAID, is a method of keeping content on several hard disks at the same time. A RAID could be software or hardware depending on the hard drives that are used - physical or logical ones, but what is common between them is the fact that they all perform as a single unit where information is stored. The top advantage of employing a RAID is redundancy since the data on all of the drives will be identical all the time, so even if a drive fails for whatever reason, the info will still be available on the remaining drives. The general performance is also enhanced as the reading and writing processes could be split between multiple drives, so a single one will not be overloaded. There're different kinds of RAIDs where the capabilities and fault tolerance may differ based on the specific setup - whether data is written on all the drives in real time or it is written on a single drive and afterwards mirrored on another, what number of drives are used for the RAID, and many others.