What is disk duplexing?

Which method of fault tolerance is the least expensive per MB of storage disk duplexing or disk striping with parity?

• Answer:

  Disk duplexing requires writing the same data twice and requires an extra controller.Disk striping with parity only writes once and requires only one controller. Although the parity information in disk striping with parity does take up some space, it does not take up as much space as the duplicate data in disk duplexing.therefore,disk duplexing is more expensive.