RAID, which is an acronym of Redundant Array of Independent Disks, is a software or hardware storage virtualization technology which enables a system to use multiple hard drives as a single logical unit. Simply put, all drives are used as one and the information on all of them is identical. This kind of a configuration has two major advantages over using a single drive to save data - the first one is redundancy, so in the event that one drive fails, the information will be accessed through the remaining ones, and the second one is improved performance because the input/output, or reading/writing operations will be distributed among several drives. There are different RAID types depending on the number of drives are used, whether reading and writing are both executed from all the drives at the same time, if data is written in blocks on one drive after another or is mirrored between drives in the same time, etcetera. According to the exact setup, the error tolerance and the performance may vary.