Patent ID: 7219256

Claim:
A method for controlling data storage in a data storage system having a cache memory and a back end storage, said method comprising: in response to a detection of an event failure during an input/output (I/O) request from a host data processing system to said data storage system, sending a copy of data associated with said I/O request to said cache memory, and forwarding said data associated with said I/O request to said back end storage data; determining whether or not there is an acknowledgement from said back end storage regarding the receipt of said data associated with said I/O request; and in response to a determination that there is an acknowledgement from said back end storage regarding the receipt of said data associated with said I/O request, flushing said data associated with said I/O request from said cache memory; and routing said acknowledgement to said host data processing system; in response to a determination that there is no acknowledgement from said back end storage regarding the receipt of said data associated with said I/O request, determining whether or not a retry operation needs to be performed; and in response to a determination that no retry operation is needed, notifying said host data processing system of said event failure.