Electrical computers and digital processing systems: memory – Storage accessing and control – Specific memory composition
Reexamination Certificate
1999-10-21
2002-09-24
Gossage, Glenn (Department: 2187)
Electrical computers and digital processing systems: memory
Storage accessing and control
Specific memory composition
C711S114000, C711S162000, C360S047000, C369S030010, C369S030190, C369S030200, C714S006130
Reexamination Certificate
active
06457096
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a redundant recording disk device and a data processing method used therefor, and more particularly, to a disk device providing shortened access time and having improved fault resistance by performing redundant recording. The present invention also relates to a method of data writing/reading processing performed in the disk device.
2. Description of the Background Art
In a data processing system, a large problem is that information written into a disk device cannot be read out because of a fault or the like.
As measures to solve the problem, a technique referred to as RAID (Redundant Array of Inexpensive Disks) conventionally exists, which copes with the problem by providing a plurality of disk devices in a data processing system and writing predetermined redundant data into the plurality of disk devices.
The RAID system is for restoring, when one of the plurality of disk devices cannot be accessed upon failing, data recorded in the failing disk device on the basis of data recorded in the remaining disk devices.
As a system using a single disk device, a disk device for performing redundant recording, that is, writing mirrored data on the same track on a recording surface of a disk (a recording medium in the disk device) is disclosed in Japanese Patent Laying-Open No. 6-267195 (hereinafter referred to as a prior document).
According to the disk device described in the prior document, by performing the redundant recording, even when one of the data that is mirrored and recorded cannot be accessed because a fault occurs in a part of the disk, a deficit in the recorded data can be avoided by accessing the other recorded data. In the disk device described in the prior document, when no fault occurs in the disk, the performance of the disk device can be improved by reducing rotational latency in data reading by half.
In order to use the above-mentioned RAID system, however, a large-scale data processing system which is provided with a plurality of disk devices must be constructed. Therefore, it cannot be said that the RAID system is useful in all system environments.
Also, in the disk device described in the prior document, the redundant recording is performed on the same recording surface. When a fault occurs in the whole of one recording surface by a fault in a recording head or the like, therefore, it is impossible to avoid a deficit in information.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a disk device capable of continuing practical use as a disk device even when one recording surface is not usable because of a fault, although it is a single disk device, and increasing the access speed of a disk when there is no fault, and a data processing method used therefor.
The present invention has the following features to achieve the above-mentioned object.
A first aspect of the present invention is directed to a redundant recording disk device for writing data to and reading data from parallel tracks on a plurality of disks, comprising:
a plurality of disks which are rotated in synchronization with each other;
a plurality of recording heads respectively corresponding to the plurality of disks for writing and reading data to and from respective recording surfaces among the disks; and
control means for controlling the positions of the recording heads on the recording surfaces and the writing and reading of the data,
the control means carrying out, when arbitrary data is written, control such that mirrored data are written into positions on the same cylinder, i.e., a corresponding radius, on the plurality of disks, on the different recording surfaces, and having a predetermined phase difference around respective rotation axes of the plurality of disks, while carrying out, when the written arbitrary data is read out, control such that the mirrored data which have been written into the different recording surfaces are read out in a parallel manner.
As described above, in the first aspect, a mirrored pair of data are written into two different disks (recording surfaces), respectively, for each data to be written. Even if either one of the disks cannot be accessed upon failing, therefore, the other disk can be accessed to read out the data. Further, the data are read out in a parallel manner. In a normal case where there is no fault, therefore, read time is shortened, thereby making it possible to read out the data at higher speed.
According to a second aspect, in the first aspect, the plurality of disks are divided into two groups by the recording surface when the disks are even in number, and the two groups are respectively constructed as logical disks,
the control means carrying out control such that the mirrored data are written and read to and from the two logical disks constructed.
As described above, in the second aspect, the content of one disk is logically divided into two, to constitute two logical sub-disks in the first aspect. The mirrored data are written into the two logical sub-disks (recording surfaces) for each data to be written. Even if either one of the disks cannot be accessed upon failing, therefore, the other disk can be accessed to read out the data. Further, the data are read out in a parallel manner. In a normal case where there is no fault, therefore, read time is shortened, thereby making it possible to read out the data at higher speed. Further, when a reading block is large, the speed at which the data are read out of the disk (the recording surface) is also increased.
According to a third aspect, within the first aspect, each of the recording surfaces of the plurality of disks is partitioned into two regions having the same shape and capacity, the disks are divided into two groups respectively comprising a group of the one regions and a group of the other regions over the plurality of recording surfaces, and the two groups are respectively constructed as logical disks,
the control means carrying out control such that the mirrored data are written and read to and from the two logical disks constructed.
As described above, within the third aspect, the content of one disk is logically divided into two, to constitute two logical sub-disks, within the first aspect. The mirrored data are written into the two logical sub-disks (recording surfaces) for each data to be written. Even if either one of the disks cannot be accessed upon failing, therefore, the other disk can be accessed to read out the data. Further, the data are read out in a parallel manner. In a normal case where there is no fault, therefore, read time is shortened, thereby making it possible to read out the data at higher speed.
According to a fourth aspect, within the first to third aspects, when each of the tracks on the plurality of recording surfaces is partitioned into an even number of sectors, the phase difference is 180 degrees.
According to a fifth aspect, within the first to third aspects, when each of the tracks on the plurality of recording surfaces is partitioned into an odd number of sectors, the phase difference is an angle of approximately 180 degrees at the head of the sector.
As described above, in the fourth and fifth aspects, the same data are written into positions having a phase difference of 180 degrees or approximately 180 degrees on the two different disks (logical disks). In a normal case where there is no fault, therefore, average rotational latency in data reading is reduced to half of the conventional time, and read time is also shortened, thereby making it possible to read out the data at higher speed.
A sixth aspect is directed to a data processing method for writing data to parallel tracks repeatedly passing respective positions for conversion in a plurality of disks, respectively, wherein
with respect to the plurality of disks which are rotated in synchronization with each other, mirrored data are written into positions on the same cylinder on the plurality of disks, on different recording surfaces, and have a predetermined phase di
Ageishi Narutoshi
Kato Yuichi
Suzuki Motoshi
Gossage Glenn
Wenderoth , Lind & Ponack, L.L.P.
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