Abstract: In one embodiment, a HDD creates a segment table to associate an address of user data in a flash memory with an LBA in a magnetic disk. The HDD updates the segment table in a DRAM and saves it to the flash memory at a specific timing. The HDD creates journals indicating the update of the segment table and saves it to the flash memory. The latest segment table can be restored using the segment table and the journals in the flash memory.

Abstract: Embodiments of the present invention improve efficiency in saving log data in a hard disk drive (HDD) equipped with a magnetic disk and a flash memory,. In an aspect of one embodiment of the present invention, a HDD creates a segment table to associate an address of user data in a flash memory with an LBA in a magnetic disk. The HDD updates the segment table in a DRAM and saves it to the flash memory at a specific timing. The HDD creates journals indicating the update of the segment table and saves it to the flash memory. The latest segment table can be restored using the segment table and the journals in the flash memory.

Abstract: Embodiments of the present invention help to suppress adverse effects on the host computer operation caused by saving a segment table. According to one embodiment, a hard disk drive (HDD) creates a segment table to associate addresses of user data in a flash memory with LBAs in a magnetic disk. The HDD updates the segment table in a DRAM and saves it to the flash memory at a specific timing. The HDD creates a journal indicating an update of the segment table and saves it to the flash memory. The segment table and the journal in the flash memory enable the latest segment table to be restored. If the HDD receives a predetermined command from a host computer, it saves the segment table in the DRAM into the flash memory.

Abstract: Embodiments of the invention reduce the host's wait time by controlling buffer for a data storage device. In a hard disk drive (HDD) disclosed herein, after write data from a host is stored in a write buffer, the size of a continuous free space left forward from the end position of the stored write data is detected. If the size is smaller than a criterion size, that is, the size is not large enough to store the next command's write data, the write buffer is searched for a continuous free space not smaller than the criterion size. If a continuous free space not smaller than the criterion size is detected, the HDD sets a write pointer to the continuous free space. This makes it possible to receive the next write data from the host and therefore reduce the host's wait time.