Logical track write scheduling system for a parallel disk drive array data storage subsystem

Abstract From the Canadian patent

The parallel 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 an array of redundancy groups, each containing N+M disk drives. A performance improvement is obtained by eliminating redundancy data updates in the redundancy group by writing modified virtual track instances into previously emptied logical tracks and marking the data contained in the previous virtual track instance location as invalid. Logical cylinders containing a mixture of valid and invalid virtual tracks are emptied by writing …