RAID, which stands short for Redundant Array of Independent Disks, is a software or hardware storage virtualization technology which makes it possible for a system to use many hard drives as a single logical unit. Simply put, all the drives are used as one and the info on all of them is identical. This kind of a configuration has 2 major advantages over using a single drive to save data - the first is redundancy, so in the event that one drive breaks down, the data will be accessed from the others, and the second is improved performance as the input/output, or reading/writing operations will be distributed among a number of drives. There are different RAID types based on how many drives are used, whether reading and writing are both handled from all drives simultaneously, whether data is written in blocks on one drive after another or is mirrored between drives in the same time, and many others. Depending on the particular setup, the error tolerance and the performance may vary.