Methods and structure for improved shipping of I/O requests among multiple storage controllers of a clustered storage system. Minimal processing of a received I/O request is performed in a first controller to determine whether the I/O request is directed to a logical volume that is owned by the first controller or to a logical volume owned by another controller. For requests to logical volumes owned by another controller, the original I/O request is modified to indicate the target device address of the other controller. The first controller then ships the request to the other controller and configures DMA capabilities of the first controller to exchange data associated with the shipped request between the other controller and memory of the host system.