<P> RAID 6 extends RAID 5 by adding another parity block; thus, it uses block - level striping with two parity blocks distributed across all member disks . </P> <P> According to the Storage Networking Industry Association (SNIA), the definition of RAID 6 is: "Any form of RAID that can continue to execute read and write requests to all of a RAID array's virtual disks in the presence of any two concurrent disk failures . Several methods, including dual check data computations (parity and Reed - Solomon), orthogonal dual parity check data and diagonal parity, have been used to implement RAID Level 6 ." </P> <P> RAID 6 does not have a performance penalty for read operations, but it does have a performance penalty on write operations because of the overhead associated with parity calculations . Performance varies greatly depending on how RAID 6 is implemented in the manufacturer's storage architecture--in software, firmware, or by using firmware and specialized ASICs for intensive parity calculations . RAID 6 can read up to the same speed as RAID 5 with the same number of physical drives . </P> <P> Two different syndromes need to be computed in order to allow the loss of any two drives . One of them, P can be the simple XOR of the data across the stripes, as with RAID 5 . A second, independent syndrome is more complicated and requires the assistance of field theory . </P>

B. what is the minimum number of drives required to create a striped volume