RAID, which is short for Redundant Array of Independent Disks, is a software or hardware storage virtualization technology that enables a system to use a number of hard drives as one single logical unit. To put it differently, all of the drives are used as one and the information on all of them is the same. This type of a configuration has 2 huge advantages over using just a single drive to keep data - the first one is redundancy, so in the event that one drive fails, the data will be accessed through the remaining ones, and the second one is better performance because the input/output, or reading/writing operations will be distributed among several drives. There're different RAID types depending on what amount of drives are used, whether reading and writing are both done from all of 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, and many others. Based on the particular setup, the error tolerance and the performance could differ.