US Patent 7490196 Data backup using both tape and disk storage

A magnetic tape apparatus for backup stores data provided from a computer on a magnetic tape. A writing circuit writes data provided from the computer on the magnetic tape, and switches a writing destination for data from the magnetic tape to a memory module when it is determined that data cannot be written on the magnetic tape, and writes address information and data following the data written on the magnetic tape onto the storage medium. The address information indicates a position on the magnetic tape where writing data should originally be written. A reading circuit determines a timing at which a reading source for data is switched from the magnetic tape to the storage medium according to the address information of data written on the memory module, and reads data from the magnetic tape to switch the reading source for data to the storage medium at the determined timing.