Redundant Array of Independent Disks, or RAID, is a way of keeping content on several hard drives simultaneously. A RAID might 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 one single unit where your information is kept. The main advantage of using a RAID is redundancy as the info on all of the drives is identical at all times, so even in the event that some drive fails for whatever reason, the info will still be available on the other drives. The general performance is also enhanced because the reading and writing processes will be split between a number of drives, so a single one will not be overloaded. There are different kinds of RAIDs where the efficiency and fault tolerance may vary based on the particular 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, the number of drives are used for the RAID, etcetera.