Abstract:
The invention provides for a method and associated apparatus operable in a RAID subsystem having redundant disk array controllers to assure dual, redundant cache consistency while permitting operation of the RAID subsystem in response to host computer (120)I/O requests. The methods and apparatus of the present invention provide for a process of initializing the redundant disk array controllers (118.1, 118.2) in response to a power-on reset cycle (or other similar reset cycles). The first controller (118.1) partially initializes for processing of host requests then awaits the partial initialization of the second controller (118.2). After a brief timeout awaiting the second controller (118.2), or in response to an erroneous initialization of the second controller (118.2), the first controller (118.1) configures itself to perform host computer (120) I/O requests in a write-through mode (bypassing cache operations) until the second controller (118.2) eventually initializes. Once both controllers (118.1, 118.2) are initialized, the redundant caches are synchronized. Finally, the initialized controllers having synchronized the redundant caches begin normal, mirrored, redundant operation. Until such time as the redundant caches are synchronized, the first controller (118.1) continues operations in response to host computer (120) I/O requests but with the degraded performance associated with the cache write-through mode.
Abstract:
The invention provides for a method of transferring data to a storage medium (39) arranged with a host computer (10) and which includes the steps of providing a controller (18) having a cache memory (33), generating a cache-flushing parameter in the host computer (10), transferring the cache-flushing parameter from the host computer (10) to the controller (18), and writing a quantity of write request data from the cache memory (33) of the controller (10) to the storage medium (39) in accordance with the cache-flushing parameter.