Device parity protection

Device parity protection uses a data redundancy technique that protects data by spreading the parity data across multiple disk units in the parity set. When a failure occurs on a disk unit that has device parity protection, the data is reconstructed.

To protect data, the disk IOA calculates and saves a parity value for each bit of data. Conceptually, the IOA computes the parity value from the data at the same location on each of the other disk units in the device parity set. When a disk failure occurs, the data can be reconstructed by using the parity value and the values of the bits in the same locations on the other disks. The system continues to run while the data is being reconstructed. The overall goal of device parity protection is to provide high availability and to protect data as inexpensively as possible.

Hot spare protection can be used with device parity protection. When a valid hot spare disk unit exists in the system and a device parity protected disk unit fails, the hot spare disk unit replaces the failed disk unit.