RAID, which is an acronym of Redundant Array of Independent Disks, is a software or hardware storage virtualization technology that allows a system to employ multiple hard drives as a single logical unit. In other words, all drives are used as one and the info on all of them is the same. This kind of a configuration has 2 huge advantages over using a single drive to save data - the first one is redundancy, so in the event that one drive stops working, the info will be accessible from the others, and the second one is better performance as the input/output, or reading/writing operations will be spread among multiple drives. There are different RAID types based on how many drives are used, if reading and writing are both done from all of the drives simultaneously, if data is written in blocks on one drive after another or is mirrored between drives in the same time, and many others. Determined by the particular setup, the fault tolerance and the performance could differ.