1. A storage system transferring user data within the system, comprising: a first transfer engine; a second transfer engine; a first storage device; a second storage device; a processor; and a transfer sequencer which is a device different from the processor, wherein: the processor creates transfer sequence information for indicating sequential order of transfers of user data; the transfer sequence information includes identification information on a destination and a source, storage address information of the user data at the destination and the source, and information indicating sequential order of transfers of the user data; the transfer sequencer receives the transfer sequence information created by the processor and controls the first and the second transfer engines in accordance with the transfer sequence information; the first transfer engine transfers received user data to the first storage device in accordance with an instruction from the transfer sequencer; the first storage device stores the transferred user data; the second transfer engine transfers the user data in the first storage device to the second storage device in accordance with an instruction of the transfer sequencer; and the second storage device stores the transferred user data.