Patent ID: 8694698

Claim:
A storage subsystem coupled to a host computer, the storage subsystem comprising: a disk device coupled to the host computer, capable of communicating with the host computer and storing data related to a write request from the host computer; and a storage controller configured to control the disk device; the storage controller comprising: a memory unit configured to store data communicated with the host computer and a control information of the storage controller; and a processor unit configured to control the storage controller; wherein when a first data transfer access to the memory area of the memory unit is received after a second data transfer access is started and while the second data transfer access is in process, the storage controller is configured to determine whether the first data transfer access satisfies one of the following conditions: (1) the access is a request synchronized with a host IO; or (2) the access has a remaining data transfer quantity equal to or smaller than a predetermined threshold; and prioritize the first data transfer access over the second data transfer access when the first data transfer access satisfies the one of the conditions (1) and (2).