Redundant Array of Independent Disks, or RAID, is a way of keeping content on several hard disk drives at the same time. A RAID might be software or hardware based on the drives which are used - physical or logical ones, but what’s common between them is the fact that they all work as one single unit where your information is kept. The top advantage of using a RAID is redundancy as the info on all drives is identical all the time, so even in case one of the drives fails for whatever reason, the data will still be available on the other drives. The general performance is also enhanced as the reading and writing processes could be split between multiple drives, so a single one won't be overloaded. There are different sorts of RAIDs where the functionality and fault tolerance can vary depending on the specific setup - whether information is written on all of the drives real-time or it's written on one drive and after that mirrored on another, what number of drives are used for the RAID, and many others.