RAID 6 configuration

Storage arrays with a RAID 6 configuration protect data using double parity. With RAID 6, two different sets of parity data are used (denoted by Px,y and Qx,y in the figure), allowing data to be preserved if two drives fail. Each set of parity data uses a capacity equivalent to that of one of the constituent drives. The usable capacity is C x (n - 2) where C is the drive capacity with n drives in the storage array. A minimum of four physical drives is required.

This fault tolerance configuration is most useful when data loss is unacceptable, but cost is also an important factor. This configuration provides high resiliency levels and high usable capacity at the expense of write performance. It allows any two drives in the storage array to fail without loss of data.