RAID, which is an acronym of Redundant Array of Independent Disks, is a software or hardware storage virtualization technology which allows a system to use several hard drives as one single logical unit. Simply put, all drives are used as one and the data on all of them is the same. Such a configuration has two major advantages over using a single drive to store data - the first one is redundancy, so in case one drive stops working, the data will be accessible from the others, and the second one is improved performance because the input/output, or reading/writing operations will be spread among several drives. There are different RAID types based on what amount of drives are employed, if reading and writing are both done from all the drives simultaneously, whether data is written in blocks on one drive after another or is mirrored between drives in the same time, and so on. Determined by the exact setup, the error tolerance and the performance may differ.