Redundant Array of Independent Disks, or RAID, is a way of keeping content on multiple hard disks at the same time. A RAID could be software or hardware based on the HDDs which are used - physical or logical ones, yet what’s common between them is the fact that they all function as just a single unit where information is saved. The top advantage of using a RAID is redundancy as the info on all drives shall be the same all of the time, so even in the event that a drive fails for some reason, the data will still be available on the remaining drives. The overall performance is also better because the reading and writing processes could be split between multiple drives, so a single one will not be overloaded. There are different sorts of RAIDs where the capabilities and fault tolerance may vary depending on the exact setup - whether information is written on all the drives 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.