RAID, or Redundant Array of Independent Disks, is a technology for keeping data on several hard disks which operate together as a single logical unit. The drives can be physical or logical i.e. in the aforementioned case one single drive is divided into independent ones using virtualization software. In any case, identical information is saved on all of the drives and the key benefit of employing such a setup is that if a drive fails, the data will still be available on the other ones. Using a RAID also enhances the overall performance since the input and output operations will be spread among several drives. There are several kinds of RAID based on how many hard drives are used, whether writing is performed on all of the drives in real time or just on a single one, and how the data is synced between the hard drives - whether it is written in blocks on one drive after another or all of it is mirrored from one on the others. These factors imply that the fault tolerance as well as the performance between the various RAID types could differ.