Raymond S Mcroberts

US Patent:

55967094, Jan 21, 1997

Filed:

Nov 12, 1992

Appl. No.:

8/122739

Inventors:

Milton F. Bond - Rochester MN
Brian E. Clark - Rochester MN
Raymond S. McRoberts - Rochester MN

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

G06F 1110
G06F 1120

US Classification:

39518205

Abstract:

A storage management mechanism maintains parity records on the storage units it services, and includes a status map indicating, for each data block, the location of the corresponding parity block, and the status of the data block. If a single storage unit fails, the mechanism is placed in a failure operating mode while the system continues to operate. While in failure operating mode, storage management verifies status before accessing data on the failed storage unit. If the data has not yet been reconstructed, storage management first reconstructs the data block by successively reading and accumulating an Exclusive-OR of the corresponding blocks on all other storage units in the parity group. The reconstructed data block is then stored in the location of the parity block, and the status map is updated to indicate that the block has been reconstructed. Once the data has been reconstructed, it is only necessary to read from or write to the former parity block directly.