JPH0573226A - Data input/output system for external storage device - Google Patents

Abstract

PURPOSE:To prevent the transfer of the wrong data to a host device in a system where a single logic block is divided into plural data blocks and the data are simultaneously written into the disk devices corresponding to the divided data blocks by checking the sequence and the updated/unupdated states of these data blocks within the logic block in a reading state. CONSTITUTION:A single logic block is divided into plural data blocks and a parity block ECC. Then the division numbers (the sequence of data blocks in the logic block) and the updated numbers (the updated states of data blocks) are added to the data blocks as the additional information in addition to a normal CRC. These information are written into five disks (four disks for data blocks and one disk for ECC) respectively. In a reading state, the data are recovered with use of the additional information.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to data input / output in an external storage device in which a minimum access unit (logical block) of data transferred from a host device is divided into a plurality of data blocks, which are stored in a storage medium and read out. More particularly, the present invention relates to a data input / output method in an external storage device that guarantees the validity of data in a logical block.

[0002]

2. Description of the Related Art Conventionally, for example, JP-A-62-24481.
Data input / output method in an external storage device in which data from a higher-level device is divided into a plurality of data blocks and a plurality of storage media are accessed in parallel to increase the processing speed It has been known.
In this case, parity data is created for each unit accessed in parallel, and the data is written to the parity data storage dedicated area of the storage medium in parallel at the same time when writing, and when a read error occurs when reading, The parity data is read, and the data is restored by the parity data and the successfully read data block, thereby achieving high reliability. Further, the reliability of the divided data block itself is guaranteed by adding a check code to each data block at the time of writing and checking at the time of reading.

[0003]

In the above-mentioned prior art, a check code is added to each divided data block unit in order to assure the correctness of each block and is stored. What is done is about the data of the divided data blocks themselves. For example, a logical block, which is the minimum unit of access from a higher-level device, is divided into a plurality of data blocks and stored, and when the data blocks are read, the data blocks themselves are guaranteed, but the data blocks are collected and the logical blocks are stored. When configured, the order may be out of order due to a hardware failure or the like, and it cannot be guaranteed that the data blocks of the logical block are necessarily collected in the correct order.

Further, at the time of writing a data block, when the writing state ends in a halfway state such as the update of the logical block is stopped halfway due to a power failure or the like, the check added to each data block is checked. Although an error can be detected at the time of reading by code, there is no means to detect an error in a data block that has not been updated at all, so there is a possibility that updated data blocks and unupdated data blocks may be mixed when collecting logical blocks. There is a possibility that an illegal logic block will be transferred to the host device.

As described above, in the prior art, since no means for logically guaranteeing the logical block is considered, there is a possibility that erroneous data may be transferred to the host device.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, to enable an error check of the division order of the data blocks belonging to each logical block when reading the data, and An object of the present invention is to provide a data input / output method in an external storage device capable of preventing an erroneous logical block from being transferred to a higher-level device by enabling detection of an updated / unupdated state of a block.

[0007]

To achieve the above object, the present invention divides a logical block, which is the minimum unit of data transferred from a host device, into a plurality of data blocks (physical blocks), In an external storage device that stores each data block in a corresponding storage medium at the same time (simultaneously in parallel), when the logical block is written (at the time of updating), the divided data block (in addition to the error check code) is Additional information indicating that the logical block is a divided data block is added to all the divided data blocks, and this additional information is stored in the storage medium at the same time as the data block.
Further, at the time of reading, the validity of the logical block is guaranteed by checking the additional information for all the data blocks of the data block group forming the logical block.

As the additional information, information indicating a division position of a data block within a logical block (for example, an order of divided data blocks such as a division number) can be used. Thus, when each data block is read and collected, it is possible to determine whether or not the data blocks are logically arranged in the correct order.

Further, as the additional information, in addition to the information indicating the division position, information indicating whether or not each of the data blocks has been updated in logical block units (units in which writing simultaneously occurs) (for example, update time). Alternatively, it is possible to add an update number, a version number, etc., which is counted up for each update. In this case, the external storage device is provided with a means for storing the parity data of these data blocks in addition to the plurality of divided data blocks, and at the time of reading, checks the additional information including the information indicating whether or not the data has been updated. However, when a data block in an unupdated state is detected (for example, whether all the data blocks in the logical block have the same time or the same update number), a data block other than the data block (updated) is detected. Data block) and the parity data to recover the data block in the unupdated state, thereby ensuring the validity of the logical block.

[0010]

The operation based on the above configuration will be described.

According to the present invention, when the data instructed by the host device is written to the external storage device, the logical block is divided into a plurality of data blocks, and each data block is divided into a check code and a check code. Since the information indicating the order is added, when reading the logical block, when reading all the data blocks belonging to the logical block and collecting them in the control device, each data block is in the divided order. By checking whether or not they have been collected, it is possible to prevent the logical blocks collected in an incorrect order from being transferred to the higher-level device, and improve the reliability of data.

Further, by adding the update information to the data block, it becomes possible to detect the data block in the non-updated state, the update state of the data block forming the logical block is guaranteed, and the wrong logical It is possible to prevent the block from being transferred to the host device.

[0013]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a computer system including a disk drive as an external storage device to which the present invention is applied. This computer system comprises a CPU 100, which is a central processing unit, a disk control device 200, and a disk drive device (external storage device) 300.

The disk controller 200 includes a CPU 100
The disk drive device 300 is controlled in accordance with the instruction from.

FIG. 2 shows the internal structure of the disk controller 200. The disk control device 200 divides the data received from the channel control device 201 and the channel control device 201 that controls data transfer with the CPU 100 into a plurality of data blocks, and updates each data block. A check code composed of a number, a division number, a CRC, etc. is created and added, an additional information generation / check circuit 202, an ECC generation / check circuit 203 for generating a parity for a plurality of divided data blocks, a data block, and a parity block. Data buffer 204 for storing, drive devices 310 to 31 for storing information
4. Drive controllers 210 to 214 for controlling the drive devices 310 to 314 and detecting read errors,
In addition, it is configured by a microprocessor MPU 230 that controls the entire disk control device 200.

Next, a data flow when the data requested by the CPU 100 is stored in the disk devices 310 to 314 will be described. Request data (in logical block units) from the CPU 100 is divided into a plurality of data blocks (four data blocks in this example) by passing through the additional information generation / check circuit 202 via the channel control device 201. The data block has a form in which an update number, a division number, and a CRC code are added according to the information previously designated by the MPU 230. This data block is stored in the data buffer 204 and, at the same time, sent to the ECC generation / check circuit 203 in accordance with an instruction from the MPU 230, creates a parity block for a plurality of data blocks, and, similarly to the data blocks, the data buffer 204. Stored in. Data block,
When the parity blocks are complete, the MPU 230
A write instruction is issued to each drive controller 210 to 214, and a data block (four data blocks in this example) and a parity block are simultaneously (simultaneously) written to the drive devices 310 to 314 under the control of each drive controller 210 to 214. .. Thereafter, the request data (unit of logical block) issued one after another is subjected to the same processing, and then sequentially written in the drive devices 310 to 314.

In this embodiment, 310 to 313 are used for storing data blocks and 314 is used for storing parity blocks.

A data flow when reading the drive devices 310 to 314 will be described. A read instruction from the CPU 100 is transmitted via the channel control device 201 to the M
When the PU 230 receives it, the MPU 230 issues a reading instruction to the drive controllers 210 to 214.
The drive devices 310 to 314 read the data block and the parity block and store them in the data buffer 204 according to the instructions of the drive controllers 210 to 214. At this time, each drive controller performs a CRC check on each data block, and when a read error occurs, the parity block and the normally read data block are sent to the ECC generation check circuit 203, and a read error occurs. The data block that has occurred is restored and stored again in the data buffer 204. When all the data blocks are prepared, the additional information generation check circuit 202 checks the update number and the division number according to the instruction from the MPU 230, and if normal, the additional information generation check circuit 202 deletes the additional information and the like. , CPU 10 via the channel controller 201
Is transferred to 0.

FIG. 3 shows a drive device 31 according to this embodiment.
The data formats stored in 0 to 314 are shown.
In the present embodiment, each logical block from the CPU 100 is divided into four data blocks in the additional information generation check circuit 202, and each data block has a division number (for example, 0, 1, etc.) other than the CRC check code. Information such as 2, 3, ..., which shows the order of division, and an update number (for example, information that adds +1 to the information previously added to the relevant logical block, or regardless of the logical block number, The information stored in the MPU 230) is added as additional information, and one parity block is created for each added data block. The data block and parity block including these additional information are treated as normal data when viewed from the host device.

A data guarantee method using the data block format shown in FIG. 3 will be described with reference to FIG.

Now, it is assumed that the CPU 100 gives an instruction to update the logical block A. This logical block is composed of four data blocks and one parity block. As the current (before updating) information, the partition numbers are drive devices 310, 311, 312, and 313 in that order.
The update numbers of 0, 1, 2, 3 are all version "9", for example. This state is 400.
Similarly, the logical block A of the update data is divided into four data blocks, and the drive device 3
“0”, “1”, in the order of 10, 311, 312, 313
“2” and “3” are added, the version “10” is added to all as the update number, and one parity block is further created and written in the drive devices 310 to 314. One of the points of interest of the present invention is that a malfunction may occur in the drive device itself, the drive controller, or another control circuit before the data is actually written in the drive devices 310 to 314, and the data block There is no guarantee that all are successfully written. At the time of the next read instruction, the validity of the data itself is guaranteed by the CRC check code for each data block, but if a certain data block is in an unupdated state due to some malfunction, it cannot be detected by this check code. Therefore, there is a possibility that an incorrect logical block composed of the updated data block and the unupdated data block may be transferred to the host device. One of the features of the present invention is that an unupdated block is detected by adding an update number, the block is restored, and the block is transferred to a higher-level device.

For example, it is assumed that the data block 412 is not scratched by the drive 311 due to some failure. At the time of reading the next logical block A, the data blocks 411, 413, 414 and the old data block 402,
And the parity block 415 is read. Although the check is performed by the CRC check code, the data of the old data block 402 itself is correct, so the check is normally completed and the data is stored in the data buffer 204.

The data block once stored in the data buffer 402 is sent to the additional information generation check circuit 202 according to an instruction from the MPU 230. The additional information generation check circuit 202 checks that the update numbers of the individual data blocks belonging to an arbitrary logical block must all be the same. However, 41
The update number of 1,413,414 is "10", and 40
Since the update number of 2 is "9", an error is detected and MPU2
Reported to 30. The MPU 230 uses the data block 4
11, 413, 414, and the parity block 415, the data block of 412 is ECC generation check circuit 2
Wrong data can be recovered by the CPU
The data is guaranteed even if it is logically prevented from being transferred to 100.

Another point of interest of the present invention is that after the logical block is updated, at the time of reading, each data block is collected by the data buffer 204 and transferred to the CPU 100.
At this time, even if each data block is correct, there is a possibility that the order of each data block at the time of collecting and transferring it to the higher order may be incorrect due to some malfunction.

For example, the data of the divided data blocks 411 to 414 of the logical block A is the drive device 3.
10 to 314, and stored in the data buffer 204 at the time of reading. The order of the data blocks transferred to the CPU 100 is 411, 412, 413, 414.
Must be in order. However, due to an erroneous operation, for example, when the data blocks are transferred in the order of 411, 413, 412, 414, the logical block collecting this data block is
It is unreasonable. However, according to this embodiment, when the logical block A is divided into data blocks, 0, 1, 2, 3 are added as division numbers. Further, the additional information creation check circuit 202 checks the order of the division numbers. Therefore, when the data blocks as described above are sent to the additional information creation check circuit 202 in the order of 411, 413, 412, 414, the division numbers are 0, 2, 1, 3 and are in an improper order. Is detected.

As described above, according to this embodiment, it is detected and corrected at the next read time that the data blocks that should have been written in the drive devices 310 to 314 are in the unupdated state. can do. Further, it is possible to prevent the data blocks read from the drive devices 310 to 314 from being collected in an improper order and transferred to the host device.

[0028]

As described above in detail, according to the present invention, when data is written, information such as a division number that indicates the order of division is provided to each data block obtained by dividing a logical block into a plurality of pieces. Since it was added and the order was checked at the time of reading,
It is possible to prevent the configured logical block from being transferred to the host device and improve the reliability of the data transferred to the host device.

Further, at the time of writing, information indicating an update state such as an update number is added to each data block obtained by dividing a logical block into a plurality of pieces, and at the time of next reading,
Data blocks that have not been written due to a malfunction are detected, corrected, and transferred to a higher-level device, so writing (update processing) was interrupted due to a power failure, etc.
It is possible to recover a data block in which updates are mixed and improve the reliability of data transferred to a higher-level device.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a computer system using a disk drive device as an external storage device to which an embodiment of the present invention is applied.

FIG. 2 is a configuration diagram of a disk control device to which an embodiment of the present invention is applied.

FIG. 3 is a diagram showing an example of a data format stored in a drive device according to an embodiment of the present invention.

FIG. 4 is a diagram showing an example of additional information of a data block stored in a drive device according to an embodiment of the present invention.

[Explanation of symbols]

100 CPU 200 Disk control device 201 Channel control circuit 202 Additional information creation check circuit 203 ECC creation check circuit 204 Data buffer 210-214 Drive controller 230 MPU 300, 310-314 Drive device 400 Logical block before update 401-404 Before update Data block 405 ECC 410 generated from data blocks 401 to 404 Update logical block 411 to 414 Update data block 415 ECC (parity block) CRC generated from data blocks 411 to 414 CRC Cyclic redundancy code

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihiro Uchiyama 2880 Kokuzu, Odawara-shi, Kanagawa Hitachi Ltd. Odawara factory (72) Inventor Mamoru Torochi 2880, Kunifu, Odawara, Kanagawa Hitachi Ltd. Odawara Inside the factory (72) Inventor Ikuo Kawaguchi 2880 Kozu, Odawara, Kanagawa Stock company Hitachi Ltd. Odawara factory (72) Inventor Takao Sato 1099 Ozenji, Aso-ku, Kawasaki City, Kanagawa Inside Hitachi Systems Development Laboratory

Claims (1)

[Claims] 1. An external storage device that divides a logical block, which is the minimum unit of data transferred from a host device, into a plurality of data blocks, and stores each data block simultaneously in a corresponding recording medium. A means for adding, when writing, additional information indicating that the divided data block is a data block obtained by dividing the logical block, to all the divided data blocks, and storing this additional information in the recording medium at the same time as the data blocks. And a means for ensuring the validity of the logical block by checking the additional information for all the data blocks of the data block group forming the logical block at the time of reading. Data input / output method in external storage device.