RAID, or Redundant Array of Independent Disks, is a technology of storing data on a number hard disks which function together as one logical unit. The drives could be physical or logical i.e. in the second case one single drive is divided into separate ones via virtualization software. Either way, identical data is saved on all drives and the main benefit of using this type of a setup is that in case a drive stops working, the data will still be available on the remaining ones. Employing a RAID also enhances the performance as the input and output operations will be spread among a few drives. There are several types of RAID depending on how many hard drives are used, whether writing is done on all drives in real time or just on one, and how the info is synced between the drives - whether it is recorded in blocks on one drive after another or it is mirrored from one on the others. All these factors suggest that the error tolerance and the performance between the various RAID types can vary.