A method for writing data in a storage array, which is performed by a first controller in order to deal with a data writing I/O request issued by an application I/O request unit, comprising: sending a plurality of physical storage medium write requests to a physical storage medium array (S315, S415), the plurality of physical storage medium write requests being based on the data writing I/O request issued by the application I/O request unit; examining whether a writing completion judgment condition is satisfied or not (S325, S320, S327, S420); and regarding the data writing I/O request as completed and releasing the resources corresponding to the completed one(s) of the plurality of physical storage medium write requests and the resources used by the data writing I/O request (S350, S450), if the previous examining result is yes; the method being characterized by further comprising: storing the written data and the related writing information of the uncompleted one(s) of the plurality of physical storage medium write requests in a memory (S330, S430) and deleting said written data and said related writing information after the write request is completed; wherein the writing completion judgment condition is based on a predetermined number and on a specific time period, and the method further comprises regarding the writing I/O request as completed when the number of the uncompleted one(s) of the plurality of physical storage medium write requests is not larger than the predetermined number and the specific time period is attained. sending a plurality of physical storage medium write requests to a physical storage medium array (S315, S415), the plurality of physical storage medium write requests being based on the data writing I/O request issued by the application I/O request unit; examining whether a writing completion judgment condition is satisfied or not (S325, S320, S327, S420); and regarding the data writing I/O request as completed and releasing the resources corresponding to the completed one(s) of the plurality of physical storage medium write requests and the resources used by the data writing I/O request (S350, S450), if the previous examining result is yes; the method being characterized by further comprising: storing the written data and the related writing information of the uncompleted one(s) of the plurality of physical storage medium write requests in a memory (S330, S430) and deleting said written data and said related writing information after the write request is completed; wherein the writing completion judgment condition is based on a predetermined number and on a specific time period, and the method further comprises regarding the writing I/O request as completed when the number of the uncompleted one(s) of the plurality of physical storage medium write requests is not larger than the predetermined number and the specific time period is attained. storing the written data and the related writing information of the uncompleted one(s) of the plurality of physical storage medium write requests in a memory (S330, S430) and deleting said written data and said related writing information after the write request is completed; wherein the writing completion judgment condition is based on a predetermined number and on a specific time period, and the method further comprises regarding the writing I/O request as completed when the number of the uncompleted one(s) of the plurality of physical storage medium write requests is not larger than the predetermined number and the specific time period is attained.