RAID, or Redundant Array of Independent Disks, is a technology of saving data on a number hard disks that function together as one logical unit. The drives can be physical or logical i.e. in the aforementioned case one drive is split into individual ones through virtualization software. In any case, the same information is saved on all drives and the main benefit of employing this type of a setup is that in the event that a drive fails, the data will still be available on the remaining ones. Using a RAID also improves the overall performance as the input and output operations will be spread among several drives. There are several types of RAID based on how many drives are used, whether writing is performed on all the drives in real time or just on a single one, and how the info is synchronized between the hard drives - whether it's written in blocks on one drive after another or it is mirrored from one on the others. All of these factors mean that the error tolerance and the performance between the different RAID types may vary.