Abstract

A disk drive array data storage subsystem maps between virtual and physical data storage devices and schedules the writing of data to these devices. The data storage subsystem functions as a conventional large form factor disk drive memory, using a plurality of redundancy groups, each containing n+m disk drives. The use of a pool of r shared spare disk drives in this system is enhanced by apparatus which predicts the exhaustion of the pool of spare disk drives and automatically reorders additional disk drives to replace failed disk drives in the data storage subsystem. The spare disk drive replacement scheduling system records disk drive failure data and extrapolates past failure events to a target date at which the pool of spare disk drives will be exhausted. This exhaustion date is then modified by a reorder and restocking time interval indicative of the time it takes for a repairperson to be dispatched to replace the failed disk drives and replenish the pool of shared spare disk drives. This calculated order date is then used to initiate a preventative maintenance visit by the repairperson to replace the failed disk drives before the pool of spare disk drives is exhausted.