JPH08314822A - Data storage - Google Patents

Abstract

(57) [Abstract] [Purpose] To avoid wasteful data transmission between data storage devices and reduce transmission time and processing cost. [Structure] The CRC code of the record data to be transmitted on the floppy disk set in the FDD 12 of the floppy disk device 10 on the transmitting side is obtained, and the CRC code sent from the floppy disk device 20 on the transmitting side is obtained. It is compared and collated with the CRC code of the record data. If they do not match, the record data is transmitted, and if they match, they are not transmitted. As a result, useless data transmission such as retransmission of already transmitted data can be avoided. Therefore, the amount of data transferred between the data storage devices can be reduced, and the transfer time can be shortened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for transmitting data between storage devices mutually connected by a data line.

[0002]

2. Description of the Related Art Conventionally, two or more storage devices (for example, floppy disk devices) are connected by a data line, and the storage data of one storage device is transmitted to another storage device so that the contents of the storage medium are Is being duplicated. When such processing is performed, it is preferable that the amount of data to be transmitted is small in terms of transmission time and processing cost. Therefore, conventionally, transmission data has been reduced by using a technique such as data compression. However, considering the case of actually performing data transmission (medium copying), there is already data that has already been transmitted to the other party on the medium of the transmission source (copy source), or the meaning of blank data etc. Often there is no data. Even in such a case, it is wasteful to transmit all the data on the medium of the transmission source, which is also a problem in reducing the transmission time and the processing cost.

In order to deal with such a problem, a communication system as described in, for example, JP-A-63-301344, "File Communication System" has been proposed. In this communication method, the file identifier added to the received file is managed, and the file identifier is collated with the received file on the receiving side when transferring the file. Then, by notifying the transfer source of the result, it is devised so that useless file transfer can be avoided.

[0004]

However, in this communication method, there are inconveniences such as that only the file is processed, and it is necessary to add a file identifier to each file in advance at the transfer source. there were. Therefore, an object of the present invention is to provide a data storage device that can avoid unnecessary data transmission and reduce the transmission time and processing cost.

[0005]

According to another aspect of the present invention, there is provided a data storage device connected to another data storage device by a communication line, the storage medium storing data and the other data storage device. Corresponding to each data block to be transmitted on the storage medium, a means for obtaining a data check code indicating the validity of the data contained in the block, and the data block to be transmitted. A data check code for the data block of the other data storage device
A means for receiving from the other data storage device, a means for comparing and collating the obtained data check code with the received data check code, and as a result, if the two do not match, the data block is transmitted, and if they match Achieves the above object by including transmission control means for controlling the operation so that the data block is not transmitted.

A data storage device according to a second aspect is the data storage device according to the first aspect, further comprising means for determining whether or not the data block to be transmitted on the storage medium is valid data. The transmission control means,
As a result of the determination, even when the data block to be transmitted is not valid data, the operation is controlled so as not to transmit the data block, thereby achieving the above object.

According to another aspect of the data storage device of the present invention, in the data storage device of the first aspect, the data length of the data block is made variable to achieve the above object.

According to a fourth aspect of the present invention, there is provided the data storage apparatus according to the first aspect, wherein the data block is composed only of data included in a specific file on the storage medium. In order to achieve the above purpose.

[0009]

In the data storage device according to the present invention, the data check code of the data block to be transmitted and the data check code of the corresponding data block sent from the other data storage device as the transmission destination are compared and collated. The data block is transmitted only when the two do not match. This data check code is generally used to show the correctness of the data. For example, when checking the presence or absence of data change (data transmission error) during data transfer, as long as the value of the code is the same, It is possible to determine that the data has not been changed (error). In the present invention, paying attention to such a function, the data check code is used to confirm the identity between the transmission target data on the transmission side and the existing data on the reception side.

Particularly, in the data storage device according to the second aspect of the present invention, the data block to be transmitted is further validated.
The invalidity is also determined. In addition to the case where the data check codes match, the transmission is avoided even when the data block to be transmitted is not valid. Further, in the data storage device according to the third aspect of the present invention, the data check code is compared and collated and transmitted in units of variable-length data blocks. Further, in the data storage device according to the fourth aspect, the data check code is compared and collated and transmitted only for the data block included in the specific file.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail with reference to FIGS. FIG. 1 is a block diagram showing a state in which two floppy disk devices as data storage devices according to an embodiment of the present invention are connected to each other. A floppy disk device 10, which is described as a data transmission source (copying source) in this figure, includes a central processing unit (CPU) 11 for controlling the operation of the entire device and a floppy disk (not shown) as a set storage medium. Floppy disk drive for reading and writing data (FD
D) 12 and. Further, the floppy disk device 10 stores a communication control unit 13 connected to the communication line 30 and a control program executed by the CPU 11, and stores various data necessary for the control of each unit by the CPU 11 and data processing. Memory 14 to store
And a bus 15 for connecting them to each other.

Further, the floppy disk device 20 described as a transmission destination (copy destination) is also the floppy disk device 1.
It has the same configuration as 0. That is, the CPU 21, the FDD 22, the communication control unit 23, and the memory 24 each having the same function as each of the above-described units are provided, and are connected to each other by the bus 25.

Next, the operation of each floppy disk device having the above construction will be described with reference to the flow charts of FIGS. In this embodiment, a record is used as a data block, and a so-called CRC (Cyclic Redundancy Check) code is used as a data check code for indicating the validity of the data contained in the record. All records have a fixed length.

First, the procedure of operation of the floppy disk device 10 on the transmitting side will be described with reference to FIG. CPU11
Checks whether or not there is data to be transmitted on the floppy disk (copy source FD) set in the FDD 12 (step 101). If there is transmission data (step 101; Y), the data of the first record is read from this copy source FD and the data of that record (hereinafter,
Record data. ) Has no meaning and is not valid blank data (step 1)
02). This determination can be made from the format information recorded on the copy source FD. As a result, when the record is blank data (step 102;
Y), the transmission operation is not performed, and the process proceeds to the next record (step 101).

On the other hand, when the record is not blank data (step 102; N), a so-called CRC code is obtained from the data of the record and stored in the memory 14 (step 103), and the communication control unit 13 CRC of the corresponding record data to the receiving side floppy disk device 20 via the communication line 30.
Request transmission of the code (step 104). The corresponding record is designated by the record number attached to each record.

Here, the CRC code is obtained as a remainder when the entire record data is considered as a long binary digit string and a fixed number of "0" is added to this and divided by a specific binary number. However, it is generally used as a check key for inspecting the presence or absence of data change (data transmission error) during data transfer. Then, as long as the value of this CRC code is the same, it can be determined that there is no change (error) in the data. In this embodiment, paying attention to such a function, the CRC code is used to confirm the identity between the transmission target data on the transmission side and the existing data on the reception side.

Then, in response to a request from the floppy disk device 10, the floppy disk device 20 transmits the CRC code of the corresponding record data and the communication control unit 13 receives the CRC code (step 105. Then, the CPU
11 compares the CRC code of the record data stored in the memory 14 with the received CRC code (step 106). As a result of this comparison, if the two match (step 107; Y), it is determined that the record data has already been transmitted and does not need to be transmitted, and the process for the next record is performed (step 101). On the other hand, as a result of the comparison, if the two do not match (step 107;
N), transmit the record data (step 10)
8).

This processing is repeated until there is no transmission data (step 101; N), that is, after repeating all the records on the copy source FD, and then a communication end command is transmitted (step 109) to perform communication. finish.

Next, the operation of the receiving side floppy disk device 20 will be described with reference to the flow chart of FIG.
First, the CPU 21 waits for data reception (step 2
When any data is received in 01), it is decrypted and its contents are examined. If the received data is a command requesting transmission of a CRC code (step 20)
2; N, step 203; Y), the specified record data is read from the floppy disk (copy destination FD) set in the FDD 22 and the CRC code is obtained. Also in this case, the same operation as described above is performed. CPU 21
Transmits the obtained CRC code to the floppy disk device 10 by the communication control unit 23 (step 204) and enters a data waiting state (step 201).

On the other hand, when the received data is record data (step 203; N), the CPU 21
This is written in the corresponding record on the copy destination FD (step 205), and the next data reception waiting state is set (step 201). Hereinafter, such processing is repeated. Then, by receiving the communication end command (step 202; Y), the communication operation is ended.

As described above, in the present embodiment, since the retransmission of already transmitted data or the transmission of invalid data is avoided and only the necessary data is transmitted, the transfer data amount between the floppy disk devices can be reduced. Can be reduced
The transfer time can be shortened. In the present embodiment, the floppy disk device 10 is described as the transmitting side and the floppy disk device 20 is as the receiving side. However, by providing each device with both the transmitting function of FIG. 2 and the receiving function of FIG.
Each device can be a sender or a receiver as required.

In the present embodiment, the data block (record data) has been described as having a fixed length, but it may have a variable length. In this case, a plurality of data block lengths are prepared, and the CRC code is collated for each data block, whereby data can be transmitted with an optimum block length. Further, in this embodiment, all the data on the floppy disk is transmitted in record units, but the present invention is not limited to this, and it is also possible to transmit only the data of a specific file on the floppy disk. Is. In this case, the block length to be compared is variable, and the comparison is performed from the beginning of the file.

Although a floppy disk is used as an example of the storage medium in this embodiment, the present invention is not limited to this, and other media (for example, a hard disk, a magneto-optical disk, a magnetic tape, a silicon disk, etc.) can be similarly used. Of course, it can be applied.

[0024]

As described above, according to the data storage device of the present invention, the data check code of the data block to be transmitted and the corresponding data transmitted from the other data storage device which is the transmission destination. Since the data check code of the block is compared and collated and the data block is transmitted only when the two do not match, useless data transmission such as retransmission of already transmitted data can be avoided. Therefore, it is possible to reduce the transfer data amount between the data storage devices, and it is possible to shorten the transfer time.

According to the data storage device of the second aspect,
Furthermore, the validity / invalidity of the data block to be transmitted is determined, and when the data check code matches,
Even if the data block to be transmitted is not valid, the data of the block is not transmitted, so that only valid data can be transmitted. Therefore, the amount of transfer data between the data storage devices can be further reduced, and the transfer time can be further shortened.

According to the data storage device of claim 3,
Since the data check codes are compared and collated and transmitted in units of variable-length data blocks, data can be transmitted with an optimum block length. According to the data storage device of claim 4, only the data blocks included in the specific file are compared and collated with the data check code before being transmitted, which is convenient when only the specific file is transmitted. The range that can be done will be expanded.

[Brief description of drawings]

FIG. 1 is a block diagram showing a state in which two floppy disk devices as data storage devices according to an embodiment of the present invention are connected to each other.

FIG. 2 is a flowchart for explaining the operation of the floppy disk device on the transmission side.

FIG. 3 is a flowchart for explaining the operation of the receiving-side floppy disk device.

[Explanation of symbols]

 10 Floppy Disk Device on Sending Side 11 CPU (Central Processing Unit) 12 Floppy Disk Driving Unit 13 Communication Control Unit 14 Memory 15 Bus 20 Floppy Disk Device on Receiving Side 21 CPU (Central Processing Unit) 22 Floppy Disk Driving Unit 23 Communication Control Unit 24 Memory 30 communication lines

Claims (4)

[Claims] 1. A data storage device connected to another data storage device by a communication line, the storage medium storing data, and prior to data transmission to the other data storage device,
Means for determining, for each data block to be transmitted on the storage medium, a data check code indicating the validity of the data contained in the block, and the other data storage corresponding to each data block to be transmitted. A means for receiving the data check code for the data block of the device from the other data storage device, a means for comparing and collating the obtained data check code with the received data check code, and as a result, when both do not match And a transmission control means for controlling the operation so as to transmit the data block and not transmit the data block when they match. 2. The device further comprises means for determining whether or not the data block to be transmitted on the storage medium is valid data, and the transmission control means is configured to determine that the data block to be transmitted is The data storage device according to claim 1, wherein operation control is performed so that the data block is not transmitted even when the data is not valid data. 3. The data storage device according to claim 1, wherein the data length of the data block is variable. 4. The data storage device according to claim 1, wherein the data block is composed only of data included in a specific file on the storage medium.