Redundant Array of Independent Disks, or RAID, is a way of storing content on multiple hard disks at the same time. A RAID could be software or hardware depending on the hard drives which are used - physical or logical ones, however what’s common between them is that they all perform as just one single unit where information is saved. The top advantage of employing a RAID is redundancy because the info on all drives will be identical all of the time, so even in the event that one of the drives fails for some reason, the information will still be available on the other drives. The general performance is enhanced as well 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 efficiency and fault tolerance can vary depending on the specific setup - whether your data is written on all the drives real-time or it is written on one drive and afterwards mirrored on another, the number of drives are used for the RAID, and many others.