Computer controlled optimized pairing of disk units

Abstract

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. 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. This comparison of pairs of disk units is repeated until the level of protection is optimized. Each time the computer system is started, a check is made to determine if a configuration change resulted in a lower level of protection. If so, the user is asked if he would like the disk units on the computer system to be re-paired to increase the level of protection.