Hitachi Global Storage Technologies Netherlands B.v.

Tomoyuki Oyama

Hiroshi Uchida

Satoshi Yamamoto

Tetsuo Semba

Fuminori Sai

Kei Yasuna

Toshio Kakihara

Kohji Takasaki

Hiromi Nishimiya

Akinori Yuba

Embodiments of the present invention efficiently perform servo correction for prevention of propagation of a position error in a radial direction in self servo write (SSW). According to one embodiment, in SSW, a target position of a reference track TO in writing a servo write track TN is corrected. The target position is represented as a target value of a position signal calculated from a signal read by a read element. A signal indicating a deviation (a position error) from the target position (the target value) is referred to as PES. The SSW in this example performs correction of target positions in respective tracks using an impulse response of a servo system. Consequently, it is possible to efficiently and effectively prevent the propagation of position error in the SSW.

Method of writing pattern in disk, method of following track on disk, and apparatus for writing pattern in disk

An executable command selection system and method are provided. A command is selected as the next-to-be-executed command when the execution waiting time for the command is less than or equal to a predetermined reference time. In addition, the command selected as the next-to-be-executed command has an execution waiting time greater than or equal to a scanning time. Once a command is selected as the next-to-be-executed command, calculation of execution waiting times for subsequent commands in the command queue stops. In this manner, when the number of commands in the command queue exceeds a predetermined number, the method of the present invention improves the efficiency of command execution for a storage device.

Data storage unit, executable command selection method, and data processing method

A method and system to provide a command queue re-ordering method that can make the power save and reduction in acoustic noise. The command queue re-ordering method involves calculating the value of an evaluation function, Ev=A&#xd7;T+(1&#x2212;A)&#xd7;Fun(L) (A is any number from 0 to 1, T is a latency required to execute a write command and/or read command, and Fun(L) is an evaluation function with a seek distance L) for the write command and/or read command, and selecting the write command and/or read command having the minimum value as a next command to be execute.

Data storage device, command queue re-ordering method, and data processing method and program

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Kanagawa, Japan

Tomoyuki Oyama