RAID, or Redundant Array of Independent Disks, is a technology of storing data on several hard disks which work together as a single logical unit. The drives could be physical or logical i.e. in the latter case one drive is split into different ones through virtualization software. Either way, the same data is stored on all the drives and the key benefit of employing this kind of a setup is that in the event that a drive fails, the data shall still be available on the remaining ones. Employing a RAID also boosts the performance as the input and output operations will be spread among a couple of drives. There are several types of RAID based on how many hard disks are used, whether writing is performed on all drives in real time or just on a single one, and how the information is synced between the hard drives - whether it is recorded in blocks on one drive after another or all of it is mirrored from one on the others. These factors indicate that the fault tolerance and the performance between the different RAID types can vary.