Abstract: A backup apparatus has an address conversion table for storing, in correspondence with each other, a logical address and a physical address. The backup apparatus has a sequential data count setting unit, a sequential data information acquisition unit, and a reading unit. The sequential data count setting unit sets sequential data count information indicating the number of data blocks in a sequence in the physical address in the address conversion table. The sequential data information acquisition unit, upon receiving a read request, reads the data block in the address conversion table corresponding to the leading logical address among the logical addresses requested to be read and acquires the sequential data count information set in the address conversion table. The reading unit reads a physical volume corresponding to physical addresses in a sequence in accordance with the sequential data count information acquired by the sequential data information acquisition unit.

Abstract: A storage device includes: a storage unit for storing data; a memory for storing management information; a local storage unit for storing differential data; a controller for controlling the storage device in accordance with a process comprising the steps of: updating data; updating management information; transmitting differential data to the another storage device, the differential data being the updated portions of the data which have been updated after preceding backing up of data until current backing up of data; resetting the management information after transmitting the differential data; storing, when the storage device fails transmission of the differential data to the another storage device, the differential data and the associated management information in the local storage unit; and transmitting the differential data to the another storage device at a later time after resetting of the management information.