JPH076048A - Electronic disk system - Google Patents

Abstract

PURPOSE:To disperse the danger of fault generation and to restore data in case of fault generation by connecting plural electronic disk devices which have error correction codes to an electronic disk controller. CONSTITUTION:This system is equipped with the electronic disk devices 2-6 having circuits for storing data and circuits for storing error correction codes and the electronic disk controller 1 which controls data transfer between the electronic disk devices 2-6 and external devices. While the electronic disk devices 2-5 are used to store the data, the electronic disk device 6 is used to hold vertical parity codes of those data. If a three-bit error is detected under specific conditions, the vertical parity is used to restore troubled data. The vertical parity codes are generated by the parity generating circuit 8 of the electronic disk controller 1 by exclusively ORing respective corresponding bits of the electronic disk devices 2-5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic disk system having error correction and failure recovery functions.

[0002]

2. Description of the Related Art In a conventional electronic disk system, various means are provided to improve the reliability of the system. For example, Japanese Unexamined Patent Publication No. 2-118744 describes an electronic disk device in which an error correction code generation / correction circuit checks an error. In addition, JP-A-3
In -012756, in addition to the system using the error correction code generation / correction circuit, an electronic disk system having a dual writing structure using two electronic disk devices is described.

FIG. 4 is a block diagram of these conventional electronic disk systems. Referring to FIG. 4, the electronic disk devices 102 and 103 respectively perform error checking and correction using an error correction code. The data received by the electronic disk control device 1 from the host device 100 is written in the electronic disk device 102 and simultaneously in the electronic disk device 103. Next, when an error is detected when reading the data of the electronic disk device 102, the electronic disk device 102 is disconnected and the electronic disk device 103 is used as a substitute until the failure is repaired. After the recovery of the electronic disk device 102, the contents of the memory of the electronic disk device 103 are transferred to the electronic disk device 102 via the transfer interface 111, and then the normal operation is resumed. When the electronic disk device 103 fails, the procedure opposite to the above is performed. In the conventional electronic disk system, the contents of the data are guaranteed and the reliability of the system is improved by such means.

[0004]

Among the error factors that occur in the above electronic disk device, a multi-bit error that cannot be corrected by the error correction code alone or a failure of the control unit in the electronic disk device occurs. Therefore, it may be impossible to read data, and under these circumstances, it is impossible to continue using the above-mentioned first electronic disk system. This is a serious problem especially for the following reasons.
That is, the electronic disk device uses a memory chip for the storage medium part, but since it is recognized as a disk device by the host device and is accessed by the sector address, the control part has a smaller number of memory than the normal memory system accessed by the memory address. More complex and more frequent failures. In addition, the second conventional electronic disk system has a problem that the memory capacity needs to be twice the normal capacity.

[0005]

In order to solve the above-mentioned problems, an electronic disk system of the present invention includes a plurality of electronic disk devices having a circuit for storing data and a circuit for storing an error correction code, and these electronic disk devices. An electronic disk control device is provided between the electronic disk device and the external device to control data transfer between them. Further, in this electronic disk system, the electronic disk control device has a parity generation circuit and a data restoration circuit, and a parity code is stored in any one of the electronic disk devices.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the electronic disk system of the present invention will be described in detail with reference to the drawings.

Referring to FIG. 1, an electronic disk system according to an embodiment of the present invention comprises an electronic disk control device 1 and a plurality of electronic disk devices 2-6. The electronic disk control device 1 controls the exchange between the host device 100 and the electronic disk devices 2 to 6 in sector units. In the electronic disk system of this embodiment, it is assumed that 16 bytes of data are configured as one word. As a result, when formatted with a sector length of 256 bytes, for example, one sector has data of 16 words. The electronic disk control device 1 further includes a host interface control circuit 9 for controlling an interface with the host device 100.
A lower interface control circuit 10 for controlling the interface with the electronic disk devices 2 to 6, a parity generation circuit 8 for generating a vertical parity code from the data of the lower interface control circuit 10, and a vertical direction from the parity generation circuit 8. And a unit data restoration circuit 7 for restoring the data of the failed disk using the parity code.

As shown in FIG. 2, each of the electronic disk devices 2 to 6 includes a data transmission / reception unit 21 for transmitting / receiving data to / from the electronic disk control device 1, an error correction code generation unit 22 for generating an error correction code, and The memory unit 24 stores data, an error detection / correction unit 23 that detects an error occurrence and corrects the error, and a control unit 25 that controls the inside of the electronic disk device. These electronic disk devices 2 to 6 store the data of one word, that is, 16 bytes, in each memory unit 24 by sharing 4 bytes by 4 units. Further, in these electronic disk devices 2 to 6, when storing the 4-byte data in charge in each memory unit 24, these error correction codes (hereinafter referred to as ECC) are added and stored. .

Generally, ECC is roughly classified into a cyclic code system and a linear code system, but the ECC used in each electronic disk device of this embodiment is capable of 1-bit or 2-bit error correction and 3-bit error detection. I will assume that. Thereby, for example, firstly, a 1-bit error caused by a software error is corrected, and secondly, the memory unit 2
In 4, the error is corrected when a failure occurs in up to two memory chips at the same time, and thirdly, when the 1-bit software error and the failure in two memory chips occur at the same time, the error is generated. It is possible to respond to an event such as detection. Of course, these conditions are examples, and can be appropriately selected in consideration of the balance between the hardware cost and the reliability of the electronic disk device.

Next, with reference to FIG. 2, the operation of the electronic disk device alone according to one embodiment of the present invention will be described. First, when the data transmission / reception unit 21 receives data from the electronic disk control device 1, the ECC generation unit 22 performs EC
Generate C. Then, as described above, the ECC generation unit 22
The memory unit 24 that pairs the ECC and the data generated in
To store. At this time, the control unit 25 receives the sector address from the electronic disk control device 1 and selects an appropriate memory of the memory unit 24 based on the sector address. Also, at the time of reading data, data and ECC are read from an appropriate memory of the memory unit 24 based on the sector address received from the electronic disk control device 1. At the time of this reading, the error detection / correction unit 23 checks the data and ECC to detect the occurrence of an error, and corrects if possible. Then, the data having no error or the corrected data is transferred to the electronic disk controller 1 by the data transmitting / receiving unit 21. At this time, if an error has occurred, the electronic disk control device 1 is notified via the data transmitting / receiving unit 21 that an error has occurred.

In the electronic disk device described above, for example, when an error of 3 bits or more occurs under the above conditions, the error can be detected but the error cannot be corrected. Therefore, in the electronic disk system of the present embodiment, the electronic disk devices 2-5 are used for storing data, while the electronic disk device 6 is used for holding the vertical parity code for these data. Then, when a 3-bit error in the above condition is detected, the vertical parity is used to restore the data in which the failure has occurred.

The vertical parity code used here is the exclusive OR of the corresponding bits of the electronic disk devices 2 to 5 in the parity generation circuit 8 of the electronic disk control device 1 as shown in FIG. Generated by. The generated vertical parity code is written in the electronic disk device 6 as it is when writing data, and is used by the unit data recovery circuit 7 of the electronic disk control device 1 to restore the data in which a failure has occurred when reading the data.

Next, the operation of the electronic disk system according to the embodiment of the present invention will be described with reference to FIG. When the electronic disk control device 1 receives the data from the upper device 100, this data is sent from the upper interface control circuit 9 to the lower interface control circuit 10 in units of one word (16 bytes). Lower interface control circuit 10
4 bytes of this data are stored in 4 electronic disk devices 2
5 to 5, but at this time, these data are also transferred to the parity generation circuit 8. The parity generation circuit 8 obtains a vertical parity code (4 bytes) by taking the exclusive OR of the corresponding bits of each data for these four 4-byte data as shown in FIG. Write to the disk device 6.

When reading the data written in each electronic disk device, the lower interface control circuit 10 is used.
Reads data from the electronic disk devices 2 to 5 word by word and transfers the data for one word to the host interface control circuit 9. When an uncorrectable error occurs in any of the electronic disk devices, for example, the electronic disk device 3, at the time of reading this data, or when the electronic disk device 3 becomes inoperable due to a failure of the control unit 25. In addition, the respective data of the electronic disk devices 2, 4, 5 and 6 are transferred to the upper interface control circuit 9 via the lower interface control circuit 10 and also to the unit data restoration circuit 7. The unit data restoration circuit 7 takes the exclusive OR for each bit of the data of the electronic disk devices 2, 4 and 5 and the vertical parity code of the electronic disk device 6 as in the case of generating the vertical parity code. , Restores the data that the electronic disk device 3 should hold. The restored data is transferred to the upper interface control circuit 9 as the data of the electronic disk device 3, and is processed as one word together with each data of the electronic disk devices 2, 4 and 5. Information about the failed electronic disk device (for example, which electronic disk device has a failure) is notified to the operator by means such as a console (not shown) as in the conventional electronic disk system. When the electronic disk device 6 for storing the vertical parity code fails, the data is not restored but the operator is notified.

Although the writing operation to the electronic disk device is not performed until the failed electronic disk device is recovered, the reading operation can be continued by using the data restoration function as described above. is there.

Next, after the failed electronic disk device 3 is restored, the electronic disk controller 1 operates the electronic disk device 2,
The data 4, 5, and 6 are read word by word, and the unit data restoration circuit 7 uses these data to restore all the data in the electronic disk device 3 word by word. Then, these data are transferred to the 1 through the lower interface control circuit 10.
Write word by word in the electronic disk device 3. The restoration process of the electronic disk device 3 is performed under the control of the firmware (not shown) of the electronic disk control device 1.
After the completion of the restoration process, the normal write operation and the read operation are resumed.

In this embodiment, the four data electronic disk devices and one parity storage electronic disk device constitute an electronic disk system of 16 bytes per word. This is only an example, and an electronic disk system having an arbitrary data width can be appropriately configured by using an arbitrary number of electronic disk devices as required, and an ECC used in the electronic disk device can be appropriately configured according to the system requirements. It goes without saying that you can choose.

[0018]

As described above, according to the present invention, a failure occurs in an electronic disk device by connecting a plurality of electronic disk devices having error correction codes to an electronic disk controller to form an electronic disk system. It is possible to disperse the risk of the above and correct the locally generated failure in each electronic disk device. Moreover, even for a failure that cannot be corrected in the electronic disk device (for example, a failure of the control unit in the electronic disk device), a failure occurs by using one of the electronic disk devices for storing parity. At times, data can be restored based on this parity, which has the effect of realizing a highly reliable electronic disk system.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an electronic disk system of the present invention.

FIG. 2 is a configuration diagram of an electronic disk device of the present invention.

FIG. 3 is an explanatory diagram of vertical parity code generation in the electronic disk device of the present invention.

FIG. 4 is a configuration diagram of an electronic disk system according to a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electronic disk control device 2-6 Electronic disk device 7 Unit data restoration circuit 8 Parity generation circuit 9 Upper interface control circuit 10 Lower interface control circuit 21 Data transmission / reception unit 22 Error correction code generation unit 23 Error detection / correction unit 24 Memory unit 25 Control unit 100 Upper device 101 Electronic disk control device 102, 103 Electronic disk device 111 Transfer interface

Claims (2)

[Claims] 1. A plurality of electronic disk devices having a circuit for storing data and a circuit for storing an error correction code, and located between the electronic disk device and an external device to control data transfer between them. An electronic disk system comprising an electronic disk controller. 2. An error occurs in either of the parity generating circuit for generating a vertical parity code based on the data from the electronic disk device or the data from an external device in the electronic disk controller and the electronic disk device. And a data restoration circuit that restores data by using the vertical parity code generated by the parity generation circuit, and stores the vertical parity code generated by the parity generation circuit in any of the electronic disk devices. The electronic disk system according to claim 1, wherein: