RAID
Redundant Array of Independent Disks is a technology that allows a number of physical disks (“spindles”) to be logically combined and form a larger Volume and protect the data through the use of parity. This Volume can be presented as one or more LUN’s to servers and devices.
Example: 24 600 GB spindles were configured as a RAID 5 Volume (Parity: n-1) with the overall capacity of 13.8 TB, and then presented to 3 ESXi Hosts as 4 LUN’s, each with a capacity of approximately 3.45 TB