Stuart D Plumlee

51858843, Feb 9, 1993

Jan 24, 1990

7/469611

Dennis R. Martin - Rochester MN
Michael J. McDermott - Oronoco MN
Stuart D. Plumlee - Rochester MN
Robert H. Satin - Rochester MN
Robert L. Wenger - Rochester MN

International Business Machines Corporation - Armonk NY

G06F 1120

395575

A method of pairing disk units in a computer system where mirroring is desirable is disclosed. Where possible, disk units are paired with other disk units located on a different bus. This provides the highest level of protection against inaccessible data due to data loss or failure of a component in the computer system. Where this is not possible, the remaining disk units are paired with disk units located on a different I/O processor, a different controller, or a different disk enclosure. Where none of these pairings are possible, the remaining disk units fall below the threshold level of protection and therefore cannot be paired within the segment. Any disk units that could not be paired are placed on a spare list. Several attempts are made to pair up disk units on the spare list. If all of these attempts fail, the paired disk units with the lowest level of protection are broken apart and added to the spare list, where attempts are again made to pair up the disk units on the spare list.

51670321, Nov 24, 1992

Nov 12, 1991

7/790802

Dennis R. Martin - Rochester MN
Michael J. McDermott - Oronoco MN
Stuart D. Plumlee - Rochester MN
Robert H. Satin - Rochester MN
Robert L. Wenger - Rochester MN

International Business Machines Corp. - Armonk NY

G06F 1120

395575

A method of pairing disk units in a computer system where mirroring is desirable is disclosed. Where possible, disk units are paired with other disk units located on a different bus. This provides the highest level of protection against inaccessible data due to data loss or failure of a component in the computer system. Where this is not possible, the remaining disk units are paired with disk units located on a different I/O processor, a different controller, or a different disk enclosure. Where none of these pairings are possible, the remaining disk units fall below the threshold level of protection and therefore cannot be paired within the segment. Any disk units that could not be paired are placed on a spare list. The paired disk units with the lowest level of protection are broken apart and added to the spare list, where attempts are again made to pair up the disk units on the spare list. After all units are paired, a pair of disk units is compared with other pairs of disk units to see if the level of protection can be increased by swapping mates.