JPH06124171A - Redundant disk controller - Google Patents

Abstract

(57) [Summary] (Corrected) [Purpose] To maintain the secondary disk in the redundant disk control device normally, provide the one that confirms the normality of the secondary disk and restores it during normal operation or suspension of the primary disk. . The dual disk control device has a primary disk device 4a and a secondary disk device 4b connected to each other, and writes external data to both the primary disk device 4a and the secondary disk device 4b in response to a write command and issues a read command. In response to the read command given to the duplicated disk device that sends the data read from the primary disk device to the outside, the data is read from both the primary disk device and the secondary disk device and the data read from the secondary disk device is read. It is composed of a control means 1 for suppressing transmission to the outside and an inspection means 2 for inspecting the normality from the secondary disk device 4b read by the means 1. The processing device (CPU) 3 performs a predetermined process according to a program.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dual disk controller used as a financial terminal, for example.

In recent years, high performance of computer systems,
Although high reliability is required, there is a particularly high demand for improvement in reliability of a storage device that stores a large amount of accumulated data.

In order to meet such a demand, a duplicated disk control device comprising a primary disk device used for business and a secondary disk device as a spare device is constructed, and when a failure occurs in the primary disk device, it is switched to the secondary disk device. The system has been put to practical use with improved reliability by continuing the work.

However, little consideration was given to checking the reliability of the secondary disk device itself during operation of the primary disk device.

Therefore, there is a demand for a device which can improve the reliability of the sub disk device itself and the reliability of the entire system.

[0006]

2. Description of the Related Art In a conventional dual disk controller, the same data is written in two primary and secondary disk devices at the time of writing, and the data is read from one primary disk device at the time of reading and used for processing. Therefore, only data is written to the secondary disk device, and normality is not checked by reading data from the secondary disk device during normal operation of the primary disk device.

For this reason, while the primary disk device is operating normally, operation continues without being noticed even if an abnormality occurs in the secondary disk device, and the primary disk device fails and switches to the secondary disk device. The situation was that the abnormality of the secondary disk device was discovered for the first time.

Therefore, the abnormality of the secondary disk device is unexpectedly found, and there is no way to cope with it, and the influence on the business process and the reliability of the customer when the abnormality occurs are very large.

As a countermeasure for this, only the measures such as exchanging and using the primary and secondary disk units are used depending on the day or the day of the week, which is not sufficient.

Further, since the writing to the secondary disk device during the operation of the conventional primary disk device has the same address and the same length as the primary disk device, only the writing and updating of the frequently used part is performed. However, there is a problem that the check is not performed for all sectors of the disk device.

[0011]

As described above, the prior art has no means for confirming the normality of the secondary disk device during the operation of the primary disk device. Further, since writing is limited to a portion that is frequently used, there is a problem that writing and updating is not performed on the entire disk, and improvement is desired.

The present invention has been made to solve the above problems.

The purpose thereof is to maintain the secondary disk device in a normal state at all times, so that the normality of the secondary disk device can be confirmed and restored during normal operation of the primary disk device or during suspension of the primary disk device to ensure reliability. It is to provide a high-duplex disk controller.

[0014]

FIG. 1 is a diagram for explaining the principle of a dual disk control device according to the present invention.

In order to achieve the above-mentioned object, the dual disk control device of the present invention has a primary disk device 4a and a secondary disk device 4b connected to each other and sends data from the outside in accordance with a write command to the primary disk device 4a and the secondary disk device 4b. In a duplicated disk control device that writes data to both disk devices 4b and sends the data read from the primary disk device 4a to the outside in response to a read command, when the read command is given, the primary disk device 4a and the primary disk device 4a Control means 1 for reading data from both of the secondary disk devices 4b and suppressing the sending of the data read from the secondary disk device 4b to the outside, and normality of the data from the secondary disk device 4b read by the control means 1. The inspection means 2 for inspecting the sex.

Further, for the same purpose, the invention of claim 2 is
The primary disk device 4a and the secondary disk device 4b are connected to each other, external data is written to both the primary disk device 4a and the secondary disk device 4b in response to a write command, and the primary disk device 4a is written in response to a read command. In the duplicated disk control device for sending the read data to the outside, when the control device is not accessed, the data is read from the secondary disk device 4b and the sending of the read data to the outside is suppressed. The control means 1 and the inspection means 2 for inspecting the normality of the data read from the secondary disk device 4b by the control means 1 are included.

Further, the invention of claim 3 is the above-mentioned claim 1.
In the inventions 1 to 2, when the inspection means 2 detects an abnormality of the secondary disk device 4b, the control means 1 transfers the data of the primary disk device 4a to the secondary disk device 4b to restore the contents. Composed.

[0018]

According to the present invention, the writing is performed in the duplicated disk control device provided with the primary disk device 4a and the secondary disk device 4b which continues processing in place of the primary disk device 4a when an abnormality occurs in the primary disk device 4a. Sometimes the same data is always written to the primary and secondary disk devices 4a and 4b, and when reading, the same data is also read from the secondary disk device 4b in parallel with the reading of the primary disk device 4a, and the control means 2 causes the secondary disk device 4b to read the same data. In addition to suppressing the transfer of the read data, the inspection unit 2 checks the read data to confirm the normality of the secondary disk device 4b.

As a result, the secondary disk device 4b on standby
Also checks the same data as the primary disk device 4a and can always confirm the same state as the primary disk device 4a during the operation of the primary disk device 4a, so that when an abnormality occurs, it is possible to promptly deal with it. A highly reliable dual disk controller can be provided.

In the invention of claim 2, the control means 1 is
While the primary disk device 4a is not being read / written, a diagnostic command is issued to the secondary disk device 4b to prevent the read data from being sent to the outside, and the inspection means 2 checks the read data. The normality of the disk device 4b is confirmed.

As a result, the secondary disk device 4b can be checked while the primary disk device 4a is not being accessed. Moreover, since the data check range is not limited to the range of data read from the primary disk device 4a, the reliability of the secondary disk device 4b is further improved.

Further, the invention of claim 3 is based on the above-mentioned claim 1.
In the inventions 1 to 2, when the inspection means 2 detects an abnormality in the secondary disk device 4b, the control means 1 transfers the data of the primary disk device 4a to the secondary disk device 4b to restore the contents. is there.

As a result, it is possible to deal with the occurrence of an abnormality in the data of the secondary disk device 4b, and the operability of the redundant disk control device is further improved.

In addition, according to the present invention, since the function of diagnosing each disk device can be integrated in the control means 1, the control mechanism of the disk control device main body can be simplified and the control means 1
Since the interfaces with the disk devices 4a and 4b can be made common, the structure can be simplified and a low-cost disk control device can be provided.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. It should be noted that the same or corresponding portions as those in FIG.

FIG. 2 is a block diagram showing a schematic configuration of the entire system according to an embodiment of the present invention.

This system includes a CPU 3 for performing a predetermined process according to a program, a memory 21 for storing programs and other data, a disk control channel 1 for interfacing with various devices, a disk device 4 for storing data, and a disk error. Warning indicator 2 that displays and issues an alarm
3 and other channels 22, each of which is connected to the system bus.

The CPU 3 controls the entire system according to each program, for example. The disk control information related to access and diagnosis to the disk device 4 is the C
It is generated by the PU 3 and stored in the memory 21. The address at which the disk control information is stored is notified by the CPU 3 to the disk control channel unit 1 via the system bus.

The disk control channel unit 1 is a part that fulfills the functions of the control unit 1 and the inspection unit 2, which are the features of the present invention, and controls the disk unit 4 when activated by the CPU 3. That is, the disk control channel unit 1 generates a command relating to read / write and diagnosis for the disk device 4 based on the disk control information, notifies the disk device 4 of the command, and performs diagnosis. Also, the status information regarding the state of the disk device 4 sent from the disk device 4 is received and reported to the CPU 3.

Further, the disk control channel section 1
Controls data transfer between the disk device 4 and the memory 21.

Reference numeral 21 is a memory, for example, ROM or R
It is composed of AM. The memory 21 is used to store program data, information input from the CPU 3, the disk device 4, other input / output devices, or the like, or information output to these. Commands for controlling the disk device 4 and disk control information are also stored in the memory 21.

The disk control units 4c, 4c of the disk device 4
Reference numeral d is a part for controlling access to the disks of the primary and secondary disk devices 4a and 4b. Based on the command issued from the disk control channel 1, each disk device 4
It is a well-known device that performs various controls such as read / write on a and 4b.

The status information sent from the disk control units 4c and 4d to the disk control channel 1 includes not only information indicating the operating state of the disk device 4 (processing in progress or processing end) but also information about the diagnostic result of the disk device. included.

These pieces of information are sent to and stored in the memory 21 via the disk control channel 1.

The primary and secondary disk devices 4a and 4b are well-known devices for storing required data, and the disk controller 4c and
It is recorded on the disc under the control of 4d.

Reference numeral 23 is a warning indicator, which is a well-known one which displays the situation when an abnormality occurs and gives an alarm by a lamp or a buzzer.

The other channels 22 include channels for controlling well-known devices such as a display, a keyboard and a printer.

Next, FIG. 3 is a block diagram showing the structure of the main part of the disk control channel unit 1 of this embodiment. Less than,
The configuration of the disk control channel unit 1 of this embodiment will be described with reference to the drawings.

The disk control channel unit 1 is a DMA / P
-MODE control unit 32, command analysis unit 31, disk access unit 33, timer 34, memory (buffer) 3
5, an error processing unit 36, a diagnostic flag 37, a diagnostic address register 38, and an RV / DV (receiver / transceiver) 39, which are connected by an internal bus.

The command analysis unit 31 has, for example, a processor, receives information for controlling the disk device 4 from the CPU 3 or the memory 21 via the DMA / P-MODE control unit 32, analyzes the information, and analyzes the information. This is a part for generating commands for reading / writing and diagnosing the devices 4a, 4b.

That is, it is the command analysis unit 31 that generates a read check command for the secondary disk device 4b based on a command issued from the CPU 3 for reading the primary disk device 4a.

The control commands of the disk devices 4a and 4b analyzed and generated by the command analysis unit 31 are sent to the disk access unit 33.

The DMA / P-MODE control unit 32 uses the CP
It is a part that controls the data transfer between the U3 or the memory 21 and the disk control channel unit 1.

Information relating to the start-up command issued from the CPU 3 and disk control information from the memory 21 are stored in the DMA / P.
It is input under the control of the MODE control unit 32, and is temporarily stored in the memory (buffer) 35.

The access end notifications from the disk control units 4c and 4d and the status information regarding the states of the primary and secondary disk devices 4a and 4b are transferred to the memory 21 under the control of the DMA / P-MODE control unit 32.

The DMA (Direct Memory Access) unit, which is a component of the DMA / P-MODE control unit 32, stores data between the disk device 4 and the memory 21 or between the disk control channel 1 and the memory 21. Input / output is controlled, and P-MODE (program mode) part is CPU3
Controls the exchange of data according to the command from.

The disk access unit 33 receives the command analyzed and generated by the command analysis unit 31, and receives the command from the disk device 4
This is a part for controlling the operations of the primary and secondary disk devices 4a and 4b according to the state of.

For example, the contents of the processing to be performed by the respective disk devices 4a and 4b are determined based on the command concerning the access of the disk device 4 and the command for the diagnosis transmitted from the command analysis section 31, and the processing timing is generated. , And controls each disk control unit 4c, 4d.

The timer 34 generates an interrupt for diagnosing the secondary disk device 4b. The disk controller 4d is activated by the timer 34.

The memory (buffer) 35 is, for example, a RAM.
And is used for temporarily storing a command or disk control information related to disk access from the CPU 3 or the memory 21 and status information related to an operating state of the disk device 4 input from the disk device 4.

For example, the command for disk access sent from the CPU 3 is temporarily stored in the memory (buffer) 35 under the control of the DMA / P-MODE control unit 32 and sent to the command analysis unit 31. .

The data stored in the memory (buffer) 35 is called when the DMA / P-MODE control unit 32 finishes the operation corresponding to a predetermined command and is ready for the next operation. Be done.

The error processing unit 36 handles the case where an abnormality is detected by the inspection means 2 at the time of accessing the disk, the retry is repeated, and the reading becomes impossible due to a temporary noise or the like. Then, if the data cannot be read even after retrying for a predetermined number of times, it is determined as a defective sector, a replacement sector is allocated, and the contents are copied from the primary disk device 4a for restoration.

Further, the internal state at the time of occurrence of the error is recorded, and the warning indicator 23 is notified. The structure of the error processing unit 36 is shown in FIG.

The diagnostic flag 37 is for instructing the presence / absence of diagnosis of the secondary disk device 4b. When the CPU 3 instructs the secondary disk device 4b for diagnostics, the diagnostic flag 37
Is turned on.

The diagnosis address register 38 stores a disk address for starting diagnosis of the secondary disk device 4b, and is updated every time one diagnosis operation is completed.

Reference numeral 39 is a receiver / driver. The receiver / driver 39 controls conduction / non-conduction to the system bus and the disk interface under the control of the DMA / P-MODE control unit 32, and is used to establish the bus use right. Specifically, it is used for switching for direct memory access to the memory 21 and the like.

Next, an outline of the functions of the duplicated disk control device of the present invention will be described with reference to FIGS. The details of the operation will be described later.

The disk control channel unit 1 issues a diagnosis command when diagnosing the secondary disk device 4b, and receives disk information concerning the state of the disk device 4 from the disk device 4.

Based on this, at the time of writing to the primary disk device 4a, the disk control channel unit 1 writes the same address and length data as the primary disk device 4a to the secondary disk device 4b, and the read command to the primary disk device 4a. Is issued, the secondary disk device 4b
Also, a read command without data transfer is issued, a read operation of the same address and the same length is performed, the data is checked by the error processing unit 36, and a warning indicator is displayed when an abnormality occurs. 23, and the warning indicator 23 gives a warning by a lamp or a buzzer.

Therefore, it is possible to confirm whether or not the secondary disk device 4b always maintains the same state as the primary disk device 4a while the primary disk device 4a is operating. Further, even if an abnormality occurs in the secondary disk device 4b, it can be detected during the normal operation of the primary disk device 4a, so that it can be dealt with each time, and even if the primary disk device 4a is damaged, the secondary disk device 4b can be repaired. It is possible to immediately continue the business processing by using it.

While the primary disk unit 4a is not reading / writing, the disk control channel unit 1 issues a diagnostic command to the secondary disk unit 4b,
The error processing unit 36 of the same channel unit 1 uses the secondary disk device 4
The data read from b is checked to confirm the normality of the disk device 4b.

As a result, the secondary disk device 4b can be checked while the primary disk device 4a is not being accessed. Moreover, according to such a method, it is possible to make a diagnosis evenly over all the sectors of the secondary disk device 4b, and the reliability of the secondary disk device 4b is further improved.

Further, when an abnormality occurs in the secondary disk device 4b, the error processing unit 36 retries a predetermined number of times, and when the abnormality of the data is confirmed, the disk control channel unit 1 transfers the data of the primary disk device 4a to the secondary disk device 4a. 4b
The data is transferred to and the contents are restored.

Next, the flowchart shown in FIG. 5 concerning the diagnosis operation of the secondary disk device 4b during the normal operation of the primary disk device 4a and the diagnostic operation of the secondary disk device 4b during the suspension of the primary disk device 4a of this embodiment will be described. It will be explained with reference to FIG.

In the diagnosis during the normal operation of the primary disk device 4a, the CPU 3 sets the number of the disk to be diagnosed and the diagnosis start address in the diagnosis address register 38 (step S1). Subsequently, the CPU 3 sets the diagnostic flag 3
7 is turned on (step S2). As a result, the timer 34 starts operating.

Next, the CPU 3 sets the disk control information in the memory 21 and issues a start-up command to execute DMA.
Start the / P-MODE control unit 32 (step S
3). At this time, the arrangement address of the disk control information arranged on the memory 21 is transferred to the disk control channel 1 and temporarily stored in the memory 35. Also, the timer 34 is stopped.

The activated DMA / P-MODE control unit 3
2 reads the disk control information from the memory 21 by DMA based on the arrangement address and sends it to the command analysis unit 31. The command analysis unit 31 analyzes the command included in the disk control information (step S4). That is, whether the command analysis unit 31 is a command that involves data transfer,
Alternatively, it is determined whether the secondary disk device 4b is a command for diagnosis performed while the primary disk device 4a is stopped, and the disk access unit 33 is notified of the analysis result.

When the disk access unit 33 recognizes that the command sent is a read command, it commands the disk control unit 4c to read (step S5). That is, the disk access unit 33 determines the number of the disk device 4a to be read, the disk address to start reading, and the data length based on the access command from the command analysis unit 31, and transfers the data to the disk control unit 4c. Instruct what to do.

Based on this, the disk control unit 4c of the primary disk device 4a reads the data from the area designated by the disk address and starts the transfer (step S6). The read data is directly transferred to the memory 21 under the control of the DMA / P-MODE control unit 32.

When the reading of the primary disk device 4a is completed, the disk control unit 4c displays the completion status in the memory 35.
Transfer to. The DMA / P-MODE control unit 32 adds the result of the error processing unit 36 to the information stored in the memory 35 and returns it to the memory 21 (step S7).

Subsequently, the disk access unit 33 commands the disk control unit 4d to diagnose the secondary disk device 4b (step S8). That is, the disk access unit 33, based on the command related to the access from the command analysis unit 31,
The number of the disk device 4b to be diagnosed, the length of the data to be read, the diagnostic procedure, etc. are determined, and the disk controller 4d is instructed to perform the read without data transfer.

Based on this, the disk controller 4d of the secondary disk device 4b starts reading data from the area designated by the address register 38 (step S).
9). The read data is temporarily stored in the memory 35, and the error processing unit 36 performs, for example, ECC processing.

At this time, the data stored in the memory 35 is not transferred to the memory 21 and is discarded after being subjected to error processing.

When the access of the secondary disk device 4b is completed, the disk control unit 4d displays the completion status in the memory 35.
Transfer to. The DMA / P-MODE control unit 32 adds the result of the error processing unit 36 to the information stored in the memory 35 and returns it to the memory 21 (step S10). On this occasion,
The diagnostic address register is updated.

When the above process is completed, the DMA / P-MODE control unit 32 confirms that a series of read operations is completed by C
The PU3 is notified (step S11). That is, DMA /
The P-MODE control unit 32 drives the interrupt line (not shown) to notify the CPU 3 of the channel interrupt, thereby ending the access.

This completes the diagnosis during the normal operation of the primary disk device 4a. Subsequently, the diagnosis of the secondary disk device 4b during the suspension of the primary disk device 4a will be described.

The DMA / P-MODE control unit 32 restarts the timer 34 when the access command ends (step S12). This is a preparation for diagnosing the secondary disk device 4b while the primary disk device 4a is stopped.

When the timer 34 has not accessed the primary disk device 4a and a certain period of time elapses, the DMA / PM
The ODE control unit 32 is notified that the predetermined time has passed (step S13).

As a result, the DMA / P-MODE control unit 32 activates the disk access unit 33 by using the contents of the diagnostic address register 38 as the disk address (step S14).

That is, the disk control channel unit 1 has one diagnostic flag 37 and one diagnostic address register 38, and when the diagnostic flag 37 is on, the primary disk device 4
If there is no access to a for a certain period of time, DMA / PM
The ODE control unit 32 activates the disk access unit 33.

The disk access unit 33 is a DMA / PM
Upon receiving the notification from the ODE controller 32, the disk controller 4
A command for diagnosing the secondary disk device 4b is issued to d (step S15).

The disk controller 4d starts data read from the address of the diagnostic address register 38 by the same operation as described above (step S16).

When the reading of the fixed length of the secondary disk device 4b is completed, the access is ended and the status is returned as described above (step S17).

By the above operation procedure, the diagnosis of the secondary disk device 4b in parallel with the access of the primary disk device 4a and the diagnosis of the secondary disk device 4b while the primary disk device 4a is stopped are performed.

In the above embodiment, the primary disk device 4 is used.
As an example of the method for diagnosing the secondary disk device 4b while a is inactive, the case of reading a fixed length is shown, but other diagnostic methods are: (1) primary disk device The secondary disk device 4b is continuously diagnosed until the next read command is issued to 4a.

(2) The diagnosis of the secondary disk device 4b is continued from the start of the diagnosis until the reading for a fixed time is completed.

(3) The diagnosis of the secondary disk device 4b is continued at a constant cycle after the diagnosis is started. (4) The secondary disk device 4b is continuously diagnosed after the diagnosis is started until the primary disk device 4a fails. Make a diagnosis. The method of inspecting the secondary disk device 4b during the suspension of the primary disk device 4a is not limited to the method disclosed in the above embodiment.

In the above embodiment, the secondary disk device 4 is used.
The read of b is configured so that it does not involve data transfer,
Under the control of the CPU 3, a read access involving data transfer may be performed.

In this case, the disk access unit 33 instructs the disk control unit 4d to access with data transfer, and by transferring the data, the bus control operation of the secondary disk device 4b can be confirmed.

As a result, not only the main body of the secondary disk device 4b but also the normality of the bus can be confirmed, so that the reliability is further improved.

In the above description, the functions of the control means 1 and the inspection means 2 are shared by the disk control channel section 1 and the CPU 3, but these control means 1 and inspection means 2 are used.
The channel unit 1 may perform the function of.

Next, an operation when an abnormality is detected during the diagnosis of the secondary disk device 4b and the data of the primary disk device 4a is transferred to the secondary disk device 4b will be described with reference to FIG.

First, the disk control channel unit 1 issues a normal read request to the primary disk device 4a and accesses the primary disk device 4a. At this time, the disk access unit 33 issues an access request to the secondary disk device 4b without data transfer to the control unit 4d as a command request, and the data is read from the secondary disk device 4b (step S31).

Disk control unit 4d of the secondary disk device 4b
The data read out is checked and the error processing unit 36 is notified of the end and the end result is returned (step S32).

The error processing unit 36 checks whether or not there is an abnormality in the end result sent from the error determination unit 36a (step S
33). If the result is normal end, the process branches to "end". When it is confirmed that the end result is abnormal, the retry unit 36b retries to determine whether the read error is due to temporary noise (step S3).
4).

Subsequently, it is checked whether or not the number of retries has been performed a predetermined number of times (step S35). If the number of trials has not reached the predetermined number, the process branches to step S33 to check the normality of the secondary disk device 4b again, and if there is an abnormality, the retry is repeated.

As a result of performing the trial a predetermined number of times in step 35, if the abnormality of the secondary disk device 4b is confirmed, the alternate area management unit 36c confirms the defective sector, makes the defective sector unwritable, and A free area is searched for in order to allocate the replacement sector (step S36).

When a free sector is found, a replacement sector is assigned to the defective sector (step S37).

Information is copied from the primary disk device 4a to the allocated alternate sector (step S38).

In this way, a new sector is automatically allocated to the occurrence of a defective sector and the primary disk device 4a
Data can be transferred and the same state as that of the primary disk device 4a can be maintained.

[0102]

As described above in detail, according to the control device of the present invention, an abnormality of the secondary disk device 4b can be found during the normal operation of the primary disk device 4a, and the primary disk device 4a can be detected.
All sectors of the secondary disk unit 4b can be diagnosed during the period of "a", and when a defective sector occurs, a new sector is automatically allocated and data is transferred from the primary disk unit 4a. A disk controller can be provided.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is an overall configuration diagram of an embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a disk control channel according to an embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of an error processing unit according to the present embodiment.

FIG. 5 is a flowchart showing the operation of this embodiment.

FIG. 6 is an operation flowchart when diagnosing a secondary disk according to the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 control means (disk control channel) 2 inspection means (disk control channel) 3 processing device (CPU) 4 disk device 4a primary disk device 4b secondary disk device

Claims (3)

[Claims] 1. A primary disk device (4a) and a secondary disk device (4b) are connected to each other, and data from the outside is sent to both the primary disk device (4a) and the secondary disk device (4b) in response to a write command. A duplicated disk control device for sending data read from the primary disk device (4a) to the outside in response to a write / read command, wherein the primary disk device (4a) and the secondary disk are provided when the read command is given. A control unit (1) for reading the same data from both of the devices (4b) and suppressing the sending of the data read from the secondary disk device (4b) to the outside, and the secondary unit read by the control unit (1). A duplicated disk control device comprising: an inspection means (2) for inspecting the normality of data from the disk device (4b). 2. A primary disk device (4a) and a secondary disk device (4b) are connected, and data from the outside is sent to both the primary disk device (4a) and the secondary disk device (4b) in response to a write command. A duplicated disk control device for transmitting data read from the primary disk device (4a) to the outside in response to a write / read command, wherein the secondary disk is accessed when the primary disk device (4a) is not accessed. A control unit (1) for reading data from the device (4b) and suppressing the sending of the read data to the outside, and a data unit for reading data from the secondary disk device (4b) read by the control unit (1). A dual disk control device, comprising: an inspection means (2) for inspecting normality. 3. The above-mentioned claim 1 or 2, wherein when the inspection means (2) detects an abnormality of the secondary disk device (4b), the control means (1) transfers the data of the primary disk device (4a) to the secondary disk device. A duplicated disk control device characterized by performing data transfer to a device (4b) and restoring the contents.