RAID, which stands short for Redundant Array of Independent Disks, is a software or hardware storage virtualization technology that permits a system to use many hard drives as a single logical unit. Put simply, all drives are used as one and the information on all of them is identical. This type of a setup has 2 huge advantages over using just a single drive to save data - the first one is redundancy, so if one drive stops working, the information will be accessed through the remaining ones, and the second is improved performance since the input/output, or reading/writing operations will be spread among different drives. You can find different RAID types based on the number of drives are used, whether reading and writing are both performed from all the drives concurrently, whether data is written in blocks on one drive after another or is mirrored between drives in the same time, etcetera. Determined by the exact setup, the error tolerance and the performance may vary.