Error detection/correction and fault detection/recovery – Pulse or data error handling – Digital data error correction
Reexamination Certificate
2000-08-29
2004-02-17
Chung, Phung M. (Department: 2133)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Digital data error correction
C714S752000, C714S801000
Reexamination Certificate
active
06694475
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a magnetic disk apparatus composed of an redundant array of inexpensive disks (hereinafter called RAID system) for dividing, transferring and storing data from an external device in plural magnetic disks, generating error-correcting information and storing in the magnetic disks, and a method of data transfer.
BACKGROUND ART
Initially, the RAID system is a data storage system for dividing and storing large amounts of data entering from an external device (for example, a host computer) in plural magnetic disks, so that large amounts of data can be promptly written into magnetic disks as hard disks. Hitherto, the RAID is classified into the following five kinds according to the difference in the method of dividing and storing the data in plural magnetic disks.
The first is the RAID(0) for only dividing and storing the data in magnetic disks in sector units, the second is the RAID(1) for storing same data in plural magnetic disks in duplicate, the third is the RAID(2) and RAID(3) (as classified by compiling method of error-correcting information, for example, Hamming/parity) for dividing and storing the data in magnetic disks in bit units, compiling error-correcting information at this time and storing in an exclusive magnetic disk, the fourth is the RAID(4) for dividing and storing the data in magnetic disks in sector units, compiling error-correcting information at this time and storing in an exclusive magnetic disk for error-correcting information, and the fifth is the RAID(5) for dividing the data in sector units, storing recursively in magnetic disks, and storing the error-correcting information compiled at this time recursively in magnetic disks in sector units same as other information (without using exclusive magnetic disk for error-correcting information).
Referring next to
FIG. 11
, the types of RAID, that is, RAID(0) to RAID(5) are described in detail below.
FIG. 11
shows the configurations of RAID(0) to RAID(5), in which (A) relates to RAID(0), (B) to RAID(1), (C) to RAID(2) and RAID(3), (D) to RAID(4), and (E) to RAID(5).
FIG. 11
(A) shows the RAID(0)
1
for only dividing and storing the input data in magnetic disks in sector units. In the RAID(0)
1
, plural magnetic disks (called hard disk devices (HDD) or disks)
61
to
64
are operated simultaneously, and, for example, write data
7
transferred from the host or the like is divided and stored in the disks
61
to
64
, and the data entered in the disks
61
to
64
can be transferred at high speed, but error correction of data stored in a defective magnetic disk is disabled.
FIG. 11
(B) shows the RAID(1)
2
, which stores the entered data, for example, the same data in sector units of write data
7
transferred from the host in duplicate in plural magnetic disks (disks)
65
and
66
. The RAID(1)
2
is also known as the mirrored disk, and it is the storage method of high reliability, but since the same data is stored in duplicate, the efficiency of use of hard disks is poor.
FIG. 11
(C) shows the RAID(2) or RAID(3)
3
for dividing and storing the entered data, for example, the write data
7
transferred from the host in plural magnetic disks (disks)
67
to
70
in bit units, generating error-correcting information of the stored data, and storing in a disk
71
. Between the RAID(2) and RAID(3), the manner of generating error-correcting information about the defective magnetic disk is different, for example, parity method or Hamming method.
FIG. 11
(D) shows the RAID(4)
4
for dividing and storing the entered data, for example, the write data
7
transferred from the host in plural magnetic disks (disks)
72
to
75
in sector units, generating error-correcting information for defective magnetic disk, and storing in a disk
76
.
FIG. 11
(E) shows the RAID(5)
5
for dividing and storing recursively the entered data, for example, the write data
7
transferred from the host in plural magnetic disks (disks)
77
to
81
in sector units, generating error-correcting information P for defective magnetic disk, and storing in the disks
77
to
81
recursively.
Among these RAID(0)
1
to RAID(5)
5
, in the RAID(1)
2
to RAID(5)
5
, if a trouble occurs in any one of the disks
65
to
81
, information of the defective disk is created by using the error-correcting information, and the information can be read out to an external device (for example, the host computer). In the RAID(0)
1
, the data can be transferred and written at high speed, such as video and audio data, but if any one of the disks
61
to
64
has a trouble, the data cannot be read out.
Thus, in the magnetic disk apparatus (or hard disk apparatus) composed of such conventional RAID system, except for the RAID(0), if one of the magnetic disks has a trouble, the information of the defective magnetic disk can be created from the error-correcting information, and the operation can be continued. However, except for the RAID(0), when writing data, the error-correcting information must be created from the write data, and the write time is very long as compared with the case of writing in the RAID(0) in which the job time is dividing and recording only without making error-correcting information.
When storing and reproducing large amounts of video and audio data in magnetic disks, fast transfer of mass data is needed, and usually the RAID(0) is employed. In recording or reproducing of video and audio data, although high reliability by the use of error-correcting information is required, in the RAID(0), if a trouble occurs in one of the disks
61
to
64
, data cannot be read out, and error cannot be corrected.
The invention is devised to solve the problems of the prior arts, and it is an object thereof to present a magnetic disk apparatus and a method of data transfer capable of transferring data fast, as a speed as high as in the RAID(0), when transferring and storing mass data such as video and audio data in magnetic disks by using the RAID(4) or RAID(5) capable of correcting error.
SUMMARY OF THE INVENTION
The magnetic disk apparatus as set forth in claim
1
of the invention comprises a CPU for controlling analysis and transfer of data, communication means for receiving data from an external device and issuing, error-correcting information generating means for generating error-correcting information for the information in the error-correcting information generating unit including at least the data entered from the external device, magnetic disks for storing the data in the error-correcting information generating unit including the data from the external device and its error-correcting information, high-speed storage means for temporarily storing the data from the external device, and data transfer means for transferring data by connecting the CPU and each means, in which the data entered from the external device is temporarily stored in the high-speed storage means, and when all data in the error-correcting information generating unit including the entered data is stored, all data in the error-correcting information generating unit is transferred to the magnetic disks and simultaneously transferred also to the error-correcting information generating means.
The invention thus provides the magnetic disk apparatus for storing write data from the external device in the high-speed storage means in the error-correcting information generating unit, transferring all data to magnetic disks at once when storing all data in the error-correcting information generating unit, and eavesdropping on all transferred data by the error-correcting information generating means, and therefore writing of data in the magnetic disks and creation of error-correcting information are executed simultaneously to save the error-correcting information creation time, so that the data writing time can be shortened.
In the magnetic disk apparatus as set forth in claim
2
of the invention, the high-speed storage means includes plural storage regions for storing all data in the error-correcting information generating unit including
Chung Phung M.
Matsushita Electric - Industrial Co., Ltd.
McDermott & Will & Emery
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