JPH0981328A - External storage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an external storage which can increase the data reading speed and also can fast ensure the contents of a reading error if produced. SOLUTION: This storage is provided with the storage devices 2a and 2b, the head address store parts 4a and 4b which store the head addresses when the read-write operations are finished, the error address store parts 5a and 5b which store the erroneous head addresses, and a control part 6 which controls these storage devices and store parts. The part 6 refers to the contents of the parts 4a and 4b to select and read the storage device that has the seeking time most approximate to a read request address. When the selected storage device has an error sector, the part 6 refers to the contents of the parts 5a and 5b to select and read the storage device that has the seeking time second approximate to the read request address for the error sector.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an external storage device, and more particularly to an external storage device forming a mirror system by having a plurality of storage devices.

[0002]

2. Description of the Related Art Conventionally, an external storage device of this type is characterized in that data is simultaneously written in a plurality of storage devices when writing data, and data is read from any one storage device when reading data. And

When a data write command is executed in this type of external storage device, multiple data are stored in a plurality of storage devices so that the same data is written at the same sector address.

As a result, the contents of all the storage devices become the same, so when executing a data read command in this type of external storage device, an arbitrary one is selected from a plurality of storage devices and the data is read from this. read out.

Further, when a read error or the like due to a physical defect of the storage device is detected in any selected storage device during execution of the data read command,
The content of the stored data is guaranteed by reselecting another arbitrary one storage device different from the selected storage device and reading the data therefrom.

Through the above series of operations, this type of external storage device can improve the reliability of stored data as compared with a normal external storage device having only one storage device.

A technique related to this is disclosed in Japanese Patent Laid-Open No. 63-
It is disclosed in Japanese Patent Publication No. 98871 and Japanese Patent Laid-Open No. 59-14200.

[0008]

However, in the conventional external storage device, if there is no read error or the like on the storage device, only one arbitrary storage device is operating, and therefore data read is not possible. The required speed is not much different from the speed of an ordinary external storage device having only one storage device, and no measures have been taken to reduce this speed.

Further, in the techniques disclosed in Japanese Patent Laid-Open Nos. 63-98871 and 59-14200, there is no technique for reducing the speed required for reading data from the storage device to be accessed first. Not disclosed.

On the other hand, as a technique for reducing the speed required for this data reading, Japanese Patent Laid-Open No. 167677/1987 discloses that a data reading address range is divided by the number of storage devices, and the storage devices share the seek. Techniques for reducing time are disclosed.

However, in general, data is managed as a group on the storage device as a file, and it is hard to say that it is an effective means considering that it is locally unevenly distributed on the storage device.

For example, when the address of the data to be read extends over two divided areas, it becomes necessary to operate two recording devices.

Therefore, an object of the present invention is to reduce the speed required for reading data regardless of where the data exists on the storage device, and to promptly guarantee the content even if a read error occurs. It is to provide an external storage device that can perform.

[0014]

In order to solve the above problems, the present invention provides a control means for writing the same information to a plurality of storage devices at the same time and reading the information from any one of the storage devices. An external storage device having
Position information detecting means for detecting the position information of the recording head of the storage device, and position information storage means for storing the position information of the recording head at the end of reading and writing of the storage device, the control means, On the basis of the position information read by the position information detecting means at the time of reading, the storage device having the shortest seek time up to the read request address is selected and read.

Further, when an error occurs in reading or writing of the storage device, the storage device further comprises error position information storage means for storing error position information of the recording head in which the error has occurred, and the control means includes the error position. It is characterized in that, based on the error position information read from the information storage means, another memory device is made to read the information of the error position.

[0016]

According to the present invention, the storage device having the shortest seek time to the read request address is selected and read out based on the position information of the recording head stored in the position information storage means. The seek time can be reduced regardless of where the data resides on the storage device.

Furthermore, since the error position information is read by another storage device based on the error position information of the recording head stored in the error position information storage means, the error position information can be quickly assured. .

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram of an embodiment of an external storage device according to the present invention.

The external storage device 1 detects head addresses for detecting two storage devices 2a and 2b for reading and writing data and position information (hereinafter referred to as a head address) of recording heads of the storage devices 2a and 2b. Part 3
a, 3b, head address storage units 4a, 4b for temporarily storing head addresses of recording heads at the end of reading / writing of the storage devices 2a, 2b, and storage devices 2a, 2b
When an error occurs in the reading and writing of data, the error address storage units 5a and 5b for storing the head address of the recording head in which the error has occurred for a long time, and the storage device 2a,
2b, the head address storage units 4a and 4b, and the error address storage units 5a and 5b, and a storage device control unit 6 that controls the address storage units 5a and 5b based on a command from a higher-level device (not shown).

As described above, one head address detection unit, one head address storage unit, and one error address storage unit are provided for each storage device. Although the number of storage devices is two in this embodiment, the number is not limited to two, and the number can be arbitrarily set as long as it is two or more.

Next, the operation will be described.

First, the execution of the data write command will be described. The storage device control unit 6 multiplex-records data on the storage devices 2a and 2b so that the same data is written to the same sector address, based on an instruction from the host device. This operation is known.

Next, at the end of the data writing process, the head address detection units 3a and 3b detect the current head addresses of the individual storage devices 2a and 2b, and the current head addresses are temporarily stored in the head address storage units 4a and 4b. Are stored in the memory.

If an error is detected during the data writing process, the storage device 2 in which the error is detected.
The error occurrence addresses of a and 2b are detected by the head address detection units 3a and 3b, and the error occurrence addresses are stored in the error address storage units 5a and 5b.

Next, the execution of the data read command will be described with reference to the flowchart. 2 to 4 are flowcharts showing the read operation of the external storage device.

First, referring to FIG. 2, prior to execution of the read command, the storage device control unit 6 checks the read request address from the host device (S1). Next, the storage device control unit 6 refers to the head address storage units 4a and 4b and selects the storage device 2a or 2b whose current head address is closest to the read request address (S).
2).

The addresses stored in the head address storage units 4a and 4b are different for the following reason. That is, data read is performed by any one of the storage devices 2a.
Or 2b, the head address after data read generally differs between the storage devices 2a and 2b. Therefore, the head address storage units 4a, 4
The head address stored in b is also generally different.

Next, the storage device control unit 6 refers to the error address storage unit 5a or 5b corresponding to the selected storage device 2a or 2b, and confirms whether or not an error sector exists in the read request address. (S
3).

If the error sector does not exist, the storage device control section 6 determines that the selected storage device 2
Data read processing is executed for a or 2b (S4). Then, it is checked whether or not an error is detected during the data reading process (S5), and if no error is detected, at the end of the data reading process, the head address detecting unit 3a or 3b corresponding to the selected storage device 2a or 2b. To detect the current head address, and at that head address, select the selected storage device 2a or 2
The contents of the head address storage units 4a and 4b corresponding to b are updated (S6).

Next, the operation when an error is detected during the data reading process will be described. In this case, the process proceeds from S5 of FIG. 2 to S11 of FIG.

Referring to FIG. 3, when an error is detected during the data reading process, the contents of the error address storage unit 5a or 5b are updated by the same procedure as the data writing process (S11).

Next, in parallel with the data processing for the addresses other than the error sector, the storage device 2a or 2b whose current head address is next to the error sector address next to the currently selected storage device 2a or 2b is subjected to normal data read processing. The error sector is selected by the same procedure and the newly selected storage device 2a or 2 is selected for the error sector.
The data of the read data is guaranteed by combining the read data from the two storage devices 2a and 2b (S12).

Next, at the end of the data reading process, the current head address is detected by the head address detection unit 3a or 3b corresponding to the selected storage device 2a or 2b, and the selected storage device 2 is detected at that head address.
head address storage units 4a, 4 corresponding to a or 2b
The contents of b are updated (S6 in FIG. 2).

Next, the selected storage device 2a or 2
If there is an error sector in the read request address by referring to the error address storage unit 5a or 5b corresponding to b (S3 in FIG. 2), the process proceeds to S21 in FIG.

Referring to FIG. 4, the storage device controller 6
Is a storage device for reading out an error sector and a non-error sector by the same procedure as above.
a and 2b are selected (S21), data is read in parallel (S22), and if no error is detected (S2)
3) The read data contents are guaranteed by combining the read data (S13 in FIG. 3).

At the end of the data reading process, the head address detecting section 3a or 3b corresponding to the selected storage device 2a or 2b detects the current head address, and the head address corresponds to the selected storage device 2a or 2b. Head address storage unit 4a,
The contents of 4b are updated (S6 in FIG. 2).

If an error is detected in S23, the process proceeds to S11 in FIG.

By the way, since only the two storage devices 2a and 2b are used in this embodiment, the third storage device 2c cannot be selected. Therefore, when there are two storage devices, if an error is detected in S23, the read operation ignores this error and continues (proceeds from S23 to S6 in FIG. 2 via S13 in FIG. 3). ), Or will be interrupted.

Therefore, the following operation can be applied when the third storage device 2c (not shown) is provided.

Referring to FIG. 3, when an error is detected during the data reading process, the contents of error address storage unit 5a or 5b are updated by the same procedure as in the data writing process (S11).

Next, in parallel with data processing relating to addresses other than the error sector, the currently selected storage devices 2a, 2
The storage device 2c whose current head address is next to the error sector address next to b is selected by the same procedure as in the normal data reading process, and the error sector is read from the newly selected storage device 2c (S1).
2) The read data contents are guaranteed by combining the read data of the three storage devices 2a, 2b and 2c (S13).

Next, at the end of the data reading process, the current head address is detected by the head address detection units 3a to 3c (3c is not shown) corresponding to the selected storage devices 2a to 2c, and the head address is selected by the head address. Head address storage unit 4a corresponding to the storage devices 2a to 2c
4c (4c is not shown) is updated (S in FIG. 2)
6).

[0043]

As described above, according to the present invention, the position information detecting means for detecting the position information of the recording head of the storage device and the position information of the recording head at the end of reading / writing of the storage device are stored. Position information storage means, and the control means is configured to select and read the storage device having the shortest seek time to the read request address based on the position information read by the position information detection means at the time of reading information. Therefore, the speed required for reading data can be shortened regardless of where the data exists on the storage device.

When a read / write error occurs,
Since it further has an error position storage means for storing the error position information of the recording head, even if a read error occurs based on the error position information, the content can be quickly assured.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of an external storage device according to the present invention.

FIG. 2 is a flowchart showing a read operation of the external storage device.

FIG. 3 is a flowchart showing a read operation of the external storage device.

FIG. 4 is a flowchart showing a read operation of the external storage device.

[Explanation of symbols]

 1 External Storage Device 2a, 2b Storage Device 3a, 3b Head Address Detection Unit 4a, 4b Head Address Storage Unit 5a, 5b Error Address Storage Unit 6 Storage Device Control Unit

Claims (5)

[Claims] 1. An external storage device having control means for writing the same information to a plurality of storage devices at the same time and reading the information from any one of the storage devices. Position information detecting means for detecting the position information, and position information storing means for storing the position information of the recording head at the end of reading / writing of the storage device are provided, and the control means has the position information detecting means at the time of reading information. An external storage device, wherein the storage device having the shortest seek time to a read request address is selected and read based on the read position information. 2. When an error occurs in reading or writing of the storage device, the storage device further comprises error position information storage means for storing error position information of the recording head in which the error has occurred, and the control means includes the error position. 2. The external storage device according to claim 1, wherein, based on the error position information read from the information storage means, information reading of the error position is performed by another storage device. 3. The external storage device according to claim 2, wherein the storage device for causing the information reading at the error position to be a storage device having a second shortest seek time after the storage device selected first. . 4. The control means operates a storage device for reading information at the error position and a storage device for reading information at a position other than the error position in parallel. The external storage device described. 5. The external storage device according to claim 2, wherein the control unit combines and outputs the information read from the two storage devices.