Abstract: A propulsion system includes at least a first propeller and a second propeller. The propulsion system further includes a first engine configured to directly driving the first propeller and a second engine configured to directly driving the second propeller. The propulsion system further includes a first electric motor provided between the first engine and the first propeller, and a second electric motor provided between the second engine and the second propeller. When the first engine is stopped, the first propeller is configured to be driven by the first electric motor that rotates by power generated by the second electric motor.

Abstract: In a first management unit for a redundant array of independent disks (RAID management unit), a shared-class setting unit receives a shared-class setting command, for example, from a host computer. If the shared-class setting command includes information about the first RAID management unit and a second RAID management unit, a shared management-information creating unit creates shared management information, writes the created shared management information onto a first disk, notifies the second RAID management unit corresponding to a second disk about the shared management information, and gives an instruction to write the shared management information onto the second disk. The second RAID management unit then writes the notified shared management information onto the second disk.

Abstract: In a RAID management apparatus, a disk determination unit accesses each of RAID devices, determines a copy source disk, and sets a pointer of the determined copy source disk into a disk management table stored in a storage unit. When an input-output (I/O) processing unit accesses a disk, if an I/O error occurs on the disk, as a result a copy source disk and a copy destination disk are switched; the I/O processing unit renews a pointer associated with the copy source disk in the disk management table stored in the storage unit, and a disk notification unit notifies that the copy source disk and the copy destination disk are switched.

Abstract: In a first management unit for a redundant array of independent disks (RAID management-unit), a shared-class setting unit receives a shared-class setting command, for example, from a host computer. If the shared-class setting command includes information about the first RAID management unit and a second RAID management unit, a shared management-information creating unit creates shared management information, writes the created shared management information onto a first disk, notifies the second RAID management unit corresponding to a second disk about the shared management information, and gives an instruction to write the shared management information onto the second disk. The second RAID management unit then writes the notified shared management information onto the second disk.