RAID, or Redundant Array of Independent Disks, is a technology of storing data on multiple hard drives which work together as one logical unit. The drives could be physical or logical i.e. in the aforementioned case a single drive is divided into different ones via virtualization software. In any case, exactly the same information is saved on all the drives and the key advantage of employing this type of a setup is that in the event that a drive fails, the data shall still be available on the other ones. Having a RAID also boosts the overall performance since the input and output operations will be spread among a couple of drives. There are several kinds of RAID dependant upon how many hard drives are used, whether writing is done on all of the drives in real time or just on one, and how the data is synchronized between the drives - whether it is written in blocks on one drive after another or it is mirrored from one on the others. These factors suggest that the error tolerance and the performance between the different RAID types may differ.