RAID, or Redundant Array of Independent Disks, is a technology of storing data on a number hard disk drives that operate together as one single logical unit. The drives could be physical or logical i.e. in the latter case one drive is split into different ones using virtualization software. Either way, exactly the same information is kept on all of the drives and the basic advantage of employing this type of a setup is that in the event that a drive stops working, the data will remain available on the remaining ones. Using a RAID also boosts the overall performance because the input and output operations will be spread among a few drives. There are several types of RAID based on how many drives are used, whether writing is done on all of the 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 of these factors show that the fault tolerance and the performance between the different RAID types can differ.