Redundant Array of Independent Disks, or RAID, is a way of keeping content on several hard disks at the same time. A RAID could be software or hardware based on the drives which are used - physical or logical ones, still what’s common between them is that they all function as just a single unit where info is saved. The biggest advantage of using a RAID is redundancy because the information on all drives will be the same at all times, so even in case one of the drives fails for some reason, the information will still be present on the rest of the drives. The overall performance will also improve because the reading and writing processes could be split between different drives, so a single one won't be overloaded. There are different types of RAIDs where the performance and fault tolerance could differ according to the exact setup - whether data is written on all the drives real-time or it's written on a single drive and then mirrored on another, what number of drives are used for the RAID, and so on.