Apparatus and method for storing data with selectable data protection using mirroring and selectable parity inhibition

摘要

A protection mechanism for use in a mass storage system for providing user selectable levels of protection against data loss wherein storage segments of a plurality of disk drives are organized into at least two functionally separate logical units and a memory management mechanism is responsive to an identification of a logical unit as selected for mirroring by writing a first copy of a data block assigned to a first storage address in a designated logical unit into the assigned storage address in the designated logical unit and writing a second copy of the data block into a second storage address in the disk drives wherein the second storage address is skewed with respect to the first storage address so that the second storage address is located in a disk drive separate from the data disk drive containing the first storage address, and writing at least one parity block containing parity information relating to the data block into a disk drive. The mechanism allows a user to select to write data blocks to the disk drives without corresponding parity information being stored in the disk drives, and to later enter the parity information.