System and method to maintain performance among N single raid systems during non-fault conditions while sharing multiple storage devices during conditions of a faulty host computer or faulty storage array controller

摘要

In order to provide redundancy of host computers and storage array controllers, and thereby protect operation of a RAID system against host computer or storage array controller failure, two single RAID subsystems are conventionally provided in a conventional active-active configuration. This means each storage array controller has electrical access to each disk in its array as well as each disk in the other controller's array. The resultant interference between the controllers in accessing the disk channels causes the active-active system to normally function at approximately 130% of the speed of a single RAID system, rather than the optimum 200% of the speed of a single RAID system. The system of this invention, FULL-SPEED ACTIVE-ACTIVE redundant RAID system, contains a normally open switch or repeater which allows access by each storage array controller only to that controller's array of disks when both host computers and storage array controllers are operating normally. This provides a speed of 200% of the speed of a single RAID system. When one host computer or storage array controller fails, the switch or repeater is automatically closed, allowing the storage array controller of the functioning subsystem to control all of the disks of both single RAID subsystems.