JPH0581141A - Duplex external storage controller - Google Patents

Abstract

PURPOSE:To constitute a duplex external storage device without performing the extension of an external storage device by compressing the data to be stored in the external storage device and performing a compact encoding for the data. CONSTITUTION:A compact encoding part 6 makes the average code length of the data received from a BUS interface part 5 small by using a compact encoding method (compression) and has a function passing compressed data to an external storage device control part 7 and a function restoring compressed data received from the external storage device control part 7 to a normal code form (elongation). The external storage device control part 7 has functions performing an interface of the data compressed by the compact encoding part 6 to external storage devices 8 to 11, performing an access to the external storage devices 8 to 11 inversely and performing the interface of access data to the compact encoding part 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a duplicated external storage control device used for an external storage device.

[0002]

2. Description of the Related Art In order to construct a duplex system using a conventional external storage device, the external storage device needs to have a physical capacity which is twice the total storage data amount.

On the other hand, from the viewpoint of improving the reliability of the information processing apparatus, a method of duplicating an external storage device is adopted.

[0004]

However, in the conventional external storage device duplication method, two external storage devices having the same capacity are prepared in order to realize the redundancy of the external storage device called duplication. One of them is used for normal data storage, and the other is used as a backup or mirror image device that is completely invisible to software, so it must be an external storage device that stores exactly the same data as each other. There is a problem in that only half of the data capacity that can be physically stored is used, but only half can be used in software.

In view of the above-mentioned drawbacks, a technical object of the present invention is to provide a duplicated external storage control device constituting a duplicated external storage device without adding an external storage device.

[0006]

According to the present invention, there is provided compact encoding means for compressing data to be stored in an external storage device, and redundantly configuring the external storage device. A dual external storage controller is obtained.

Further, according to the present invention, data storage means (1) for storing predetermined data, and data for processing the data stored in the data storage means via the common signal line (3) A processing means (2), a common signal line control unit (4) for controlling the common signal line and transferring the data, and a data coding control for coding the data via the common signal control unit. Duplex external storage comprising means (6) and external storage device control means (7) for storing the encoded data encoded by the data encoding means in external storage means (8-11). A controller can be obtained.

Further, according to the present invention, a plurality of external storage device groups are connected to the redundant external storage control device, and the external storage device groups are stored in the data storage device and the data storage device. A duplicate external storage system is obtained which has a backup device that stores the same data as the above-mentioned data.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

Reference numeral 1 denotes a memory unit, which has a function of storing data processed by a central processing unit 2 which will be described later, or storing processed data. The data storage format in the memory unit 1 is a code format such as ASCII code, JIS code, or EBCDIC code, which is easy to process in the information processing apparatus.

The central processing unit 2 has a function of processing the data stored in the memory 1.

The common signal line 3 is a signal lead line for commonly connecting the memory unit 1 and the central processing unit unit 2 and the like.
It is generally called "BUS".

The BUS controller unit 4 has a function of requesting arbitration of the right to use the common signal line 3 of the memory unit 1 and the central processing unit unit 2 and performing access control.

The BUS interface unit 5 has a function of interfacing the data of the memory unit 1 and the central processing unit unit 2 etc. to the compact encoding unit 6 described below under the control of the BUS controller unit 4, and conversely, the compact unit described later. It also has a function of interfacing data from the encoding unit to the memory unit 1 and the central processing unit unit 2.

The compact encoding unit 6 reduces the average code length of the data received from the BUS interface unit 5 by using a compact encoding method described later (hereinafter referred to as compression), and an external storage device described later. Control unit 7
To the compressed data received from the external storage device control unit 7, which will be described later, in a normal code format (AS
It has a function of returning to CII code, JIS code, EBCDIC code, etc. (hereinafter referred to as decompression).

The external storage device section 7 stores the data compressed by the compact encoding section 6 in the external storage devices 8 to 1 described later.
1 to the external storage device, or vice versa
1 has a function of accessing 1 and interfacing access data to the compact encoding unit 6.

The external storage devices 8 to 11 are generally used in information processing devices such as hard disks / floppy disks / magneto-optical disks / semiconductor disks, and a plurality of external storage devices having the same specifications and the same capacity are connected. To do.

The operation of the compact encoder 6 in FIG. 1 will be described further.

At present, the format of data to be processed in an information processing apparatus such as an electronic computer is, for example, A in view of easiness of interface between different information processing apparatuses.
SCII code, JIS code, or EBCDIC
Codes such as codes are used.

However, these code formats are not optimum from the viewpoint of coding efficiency in the meaning of code length. That is, an information source (for example, data to be stored in the external storage devices 8 to 11) has a code that can minimize the storage space occupied by the information source element (for example, 'A', "B", ..., This can be assigned to sequences such as'AA ',' AB ', or words). This is, for example,
It can be proved also by "Shannon's first basic theorem" in information theory. A code that has undergone such processing will be temporarily called a compact code.

In FIG. 1, the compact encoding unit 6 has the functions of performing the above-described compact encoding (compression) and restoring it (decompression). The compact coding method includes, for example, the Huffman method, the arithmetic compression method, the LZSS method,
The LZW method and methods combining these methods are generally known. For example, a simple example of the Huffman coding method will be described with reference to FIGS. 2 and 3.

In FIG. 2, the information source elements are alphabets'A 'to'F', and the probability of their appearance (for example, in English,
When the appearance frequency in the data in the database) is given, an example in which Huffman coding is performed using the binary tree method of FIG. 3 is shown. This is because a character that often appears in an information source ('A' in this example) has a short code length (1b).
The code word ('0') of it) is assigned, and the code word ('111') of a long code length (3 bits) is assigned to the character that hardly appears, for example, 'F'. Then, it can be seen that the average code length is 2 bits, which is smaller than the 3 bits required to represent the 6 characters'A 'to'F'. This shows the effect of reducing the occupied storage capacity in the external storage devices 8 to 11 of FIG. 1, and the data stored in the memory unit of FIG.
11 shows that the storage capacity can be reduced to 2/3 as compared with the case of storing in 11.

In this embodiment, the Huffman coding method is adopted as the compact coding method as described above. However, in practical use, a compact coding method which can always obtain a double compression efficiency should be found. Is possible.

Therefore, the external storage devices 8 to 1 in FIG.
Since the data stored in No. 1 occupies only half the storage capacity if the above-mentioned compression is performed, four external storage devices 8-11, which were required four, can be essentially two 8-9. It is possible. Particularly in recent years, from the viewpoint of improving the reliability of the information processing apparatus, a method of duplicating an external storage device (one for normal data storage and the other for backup storing exactly the same data) has become important.
If you can use 10 to 11 external storage devices for backup, you can add external storage devices without
A dual system can be constructed.

Further, in this patent, it is possible to disable the compact encoding unit 6 so that the data can be stored in the external storage devices 8 to 11 in a normal data format.

[0027]

As described above, according to the present invention, since the compact encoder is used to reduce the average code length, the redundant external storage device can be constructed without adding an external storage device. Has the effect.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a simple example of Huffman coding.

FIG. 3 is a diagram showing a Huffman binary tree required for generating the code word of FIG.

[Explanation of symbols]

 1 Memory Section 2 Central Processing Unit Section 3 Common Signal Line Section 4 BUS Controller Section 5 BUS Interface Section 6 Compact Encoding Section 7 External Storage Device Control Section 8-11 External Storage Device

Claims (3)

[Claims] 1. An external storage control device comprising compact encoding means for compressing data to be stored in the external storage device, and redundantly configuring the external storage device. 2. Data storage means for storing predetermined data, data processing means for processing the data stored in the data storage means via a common signal line, control of the common signal line and the A common signal line control unit for passing data, a data coding control unit for coding the data via the common signal control unit, and an external storage for the coded data coded by the data coding unit. A dual external storage control device, comprising: external storage device control means for storing in the means. 3. The redundant external storage control device according to claim 2, wherein a plurality of external storage device groups are connected, and the external storage device group comprises a data storage device and data stored in the data storage device. A dual external storage system having a backup device storing the same data as the above.