Hitachi, Ltd.

Hitachi Global Storage Technologies Netherlands B.v.

Yoshihisa Kamo

Hitoshi Kakuta

Atsushi Tanaka

Akira Yamamoto

Kouji Arai

Hiroyuki Kitajima

Yosuke Seo

Hajime Aoi

Naoki Sato

Masahiro Kitada

Tooru Takeura

Kazuhiro Momata

Yasuhide Ouchi

Yasuhiro Katoh

Yoshito Tsunoda

Hiromichi Fujisawa

Shinichi Arai

Masao Katsumata

Zenji Tsutsumi

Tsunetaka Komachiya

Takeshi Maeda

Yoshifumi Takamoto

Makoto Saito

Hitoshi Nakamura

Hideo Tanabe

Hiroki Kanai

Makoto Koizumi

Takehiko Hamaguchi

Shunichi Torii

Noboru Shimizu

Hideaki Maeda

Toyohiko Kagimasa

Ikuya Tagawa

Reijiro Tsuchiya

Minoru Kosuge

Nobumasa Nishiyama

Hiroshi Yasuoka

Yukiya Shimizu

Kazuyoshi Adachi

Tetsuo Yuki

Toshikane Yoshimatsu

Hiroshi Maejima

Akihiko Ohba

Mitsuo Ohyama

Tosuke Seo

Embodiments of the invention prevent a decrease in magnetization or demagnetization from occurring to recording magnetization regardless of a direction in which a stray field is applied. In one embodiment, an apparatus for data storage system comprises a head having a magnetic field shield in the vicinity of a main pole, and a cover of the device, using a constituent material with a magnetic field shielding effect, across the cover, or at part thereof. When a stray field in a direction perpendicular to a recording medium is applied, the effect of the magnetic field is alleviated by the magnetic field shield installed in the vicinity of the main pole. In such a case, it need only be sufficient to form the magnetic field shield in a shape optimum for removing the stray field in the perpendicular direction only. When a stray field in a direction horizontal in relation to the recording medium is applied, the magnetic field acting on the recording medium is removed by the cover of the device comprising a magnetic component.

Perpendicular hard disk drive resistive against external magnetic field

A data storage system connectable to a host unit which issues data read/write requests to the data storage system, and which includes a plurality of disc units, and a controller connected to the disc units. A fault can occur in any of the disc units. The disc units store data in a plurality of data groups and error correcting data corresponding to each of the data groups. The controller, operable in different modes, performs processing of reconstructing data stored in any of the disc units in which a fault has occurred based on all other data belonging to any of the data groups to which the data to be reconstructed belongs and error correcting data corresponding to any of the data groups to which the data to be reconstructed belongs, and performs processing of data read/write requests from the host unit.

Data reconstruction method and system wherein timing of data of data reconstruction is controlled in accordance with conditions when a failure occurs

When receiving a write request from a processor, a control unit checks the condition of existence (or the presence/absence) in a cache for information necessary for generation of an updated value of a parity record, receives write data and reports the completion of the write request to the processor. In asynchronism with the write request from the processor, the control unit performs a load process for that information among the information necessary for generation of the updated value of the parity record which may be prepared in asynchronism with the write request from the processor and a write after process for the updated value of the parity record.

Storage unit subsystem

With respect to the disk drives provided power from a single power source in a disk drive system, start up power is first supplied to a first start-up group of the disks, preferably comprising all of the master disks, with the size of the group being selected so that the required current does not exceed the capacity of the power source. When the disk drives of the first group have substantially reached steady state, start-up is conducted with respect to a second start-up group of the disk drives so that the current required during start-up for the second group and the current required for steady state drive of the first start-up group does not exceed the capacity of the power source. With respect to each start-up group, the number of disk drives is the maximum integer value and decreases or remains the same with respect to subsequent start-up groups. When simultaneously transferring subdivided data in parallel to all of the disk drives of a parity group, respectively, seek operations in such a system are prevented from occurring simultaneously by offsetting the indices on the disks, by varying the seek operation start timing or by varying the head addresses for the start of reading and writing, all within one revolution, but the seek operations are ended at the same time, to reduce peak current requirements of the power source.

Disk system and power-on sequence for the same

A data storage system connectable to a host unit which issues data read/write requests to the data storage system, and which includes a plurality of disc units, and a controller connected to the disc units. A fault can occur in any of the disc units. The disc units store data in a plurality of data groups and error correcting data corresponding to each of the data groups. The controller performs processing of reconstructing data stored in any of the disc units in which a fault has occurred based on all other data belonging to any of the data groups to which the data to be reconstructed belongs and error correcting data corresponding to any of the data groups to which the data to be reconstructed belongs, and performs processing of data read/write requests from the host unit. The controller is operable in a first mode wherein the processing of reconstructing data has priority over the processing of data read/write requests, and a second mode wherein the processing of data read/write requests has priority over the processing of reconstructing data. The controller may determine whether to operate in the first mode or the second mode based on an urgency of data reconstruction, or may determine whether to operate in the first mode or the second mode in order to complete data reconstruction within a fixed time.

Data reconstruction method and system wherein timing of data reconstruction is controlled in accordance with conditions when a failure occurs

In a disk array subsystem capable of changing the data redundancy method between a duplicating method and a parity method, the load of data transfer occurring at the time of changing the data redundant method is reduced. In the disk array subsystem, since one data of the duplicated data are used for data for the parity data area, the one data secures an area for storing parity prepared from the data. With the arrangement, it is not necessary to transfer the data when the data redundancy method is changed from the duplicating to the parity method and the data transfer load is mitigated.

Method and apparatus for implementing redundancy on data stored in a disk array subsystem based on use frequency or importance of the data

Method for changing raid-level in disk array subsystem

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Musashimurayama, Japan

Yoshihisa Kamo