Abstract: A storage device includes first and second buffers. A request to write a new record from a host is received. A hash value (new S) of the new record is calculated. The hash value (new S) of the new record is checked to determine if the hash value exists in a second buffer. If the new S exists in the second buffer, the new record is compared with a record stored in the second buffer corresponding to the new S to check if the new record and the stored record in the second buffer match each other. If the new record and the stored record match each other, a pointer (a record number) is written as write data of the new record to the recording medium. The pointer points to the record already stored in any one of a recording medium and the second buffer.

Abstract: A storage device includes first and second buffers. A request to write a new record from a host is received. A hash value (new S) of the new record is calculated. The hash value (new S) of the new record is checked to determine if the hash value exists in a second buffer. If the new S exists in the second buffer, the new record is compared with a record stored in the second buffer corresponding to the new S to check if the new record and the stored record in the second buffer match each other. If the new record and the stored record match each other, a pointer (a record number) is written as write data of the new record to the recording medium. The pointer points to the record already stored in any one of a recording medium and the second buffer.

Abstract: A multilayer optical disk apparatus comprises an optical pickup that emits N (N represents an integer of two or more) laser beams of the same wavelength. The optical pickup emits the N laser beams at the same time, focuses the N laser beams on a first recording layer group alternately configured by N recording layers of the multilayer optical disk and performs a recording operation on the N recording layers at the same time. When changing the recording layers the optical pickup focuses the N laser beams on a second recording layer group configured by recording layers adjacent to the respective recording layers configuring the first recording layer group and performs a recording operation on the N recording layers at the same time.