GB2232807A

GB2232807A - Apparatus for reading data from and writing data on a data storage device

Info

Publication number: GB2232807A
Application number: GB9006826A
Authority: GB
Inventors: Yasuo Harashima
Original assignee: Tokico Ltd
Current assignee: Tokico Ltd
Priority date: 1989-05-19
Filing date: 1990-03-27
Publication date: 1990-12-19
Also published as: DE4011052A1; JPH02306473A; GB9006826D0

Description

i .>- 2 3 -7,> S (Z:;;, DATA STORAGE DISK APPARATUS AND METHOD FOR STORING

DATA

BACKGROUND OF THE INVENTION

The present invention generally relates to a data storage disk apparatus. In particular, the present invention relates to a magnetic disk storage device which is able to automatically alter access addresses to other good data blocks, after the controller has judged that data blocks on a magnetic disk contain error data.

Fig.5 is a block diagram to show a summary structure of a recent magnetic disk storage device containing a small computer system interface (SCSI). As shown by this f igure, this kind of device is composed of CPU (central processing unit) 1, bus 2 f or connecting CPU 1 and each component circuit, memory 3 for storing various kinds of data, drive circuit 4 for driving the magnetic disk, and 1/0 interface 5. The above-mentioned CPU 1 controls each component circuit of this device, and also excutes input/output processing of various kinds of data. The above-mentioned 1/0 interf ace 5 is connected to the host computer 7 by external bus 6.

In above described magnetic disk storage device, when the host computer 7 reads required data from a target track on the magnetic disk and detects an error, host computer 7 excutes the following processes:

host computer 7 (a) stops the present operation, and (b) issues a command to read the address information of the bad data block, and (c) issues a command to update the substitute data block data 1 Ir table. That is to say, the host computer 7 writes the address of the bad data block and the address of the corresponding substitute data block in the afore-mentioned data table.

After host computer 7 has executed the aforementioned processing, when host computer 7 attempts to access the bad data block, referring to the above data table, an attempt is then made to access the substitute data block.

In the foregoing, when the magnetic head accesses a data block, if a read error occurrs, host computer 7 have to stop the present operation. This problem slows processing in the host computer 7.

SUMMARY OF THE INVENTION

In consideration of the above described difficulties, It is an object of the present invention to provide a magnetic disk apparatus'having a magnetic disk which includes recording regions in which when errors are detected in data read from a target data block, fault information indicating that a target data block is bad is stored. Additionally, address information indicating the address of a substitute data block and in uuse flag information indicating whether or not a substitute data block is in use are stored in the above-mentioned recording regions.

To achieve the above objective, the magnetic disk apparatus further includes a substitution processing means in which when data is read, when the above-mentioned fault information is set, the above mentioned in use flag information of the data block pointed at by the above- 2 0 mentioned address information is examined. when the in use flag indicates that the substitute data block is not in use, permission to read data from that data block is denied, and the substitute data block is accesssd and a write process is carried out, after which the above-mentioned in use flag is modified to indicate that the substitute block is in use.

By examining the in use flag for the data block pointed at by the abovementioned address information when the fault information for the target data block data is set, efficient processing can be carried out based on whether the in use f lag is set or not. Thus, in the case when data errors have been generated, the processing burden on the host computer can be reduced.

In the following sections, a detailed description of an example of such a magnetic disk storage device will be described in detail to further clarify the enhancements offered by the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a diagram showing the structure of an address information table AITB of an example of the magnetic disk storage device of the present invention.

Fig. 2 is a diagram showing the structure of individual tracks of the magnetic disk used in the magnetic disk storage device shown in Fig. 1.

Fig. 3 and Fig. 4 are flow charts showing the operation of the magnetic disk storage device of the present invention.

Fig. 5 is block diagram of a prior art disk drive apparatus.

3 Detailed Description of the Preferred Embodiment

In the following section, a preferred embodiment of the present invention will be described with reference to the drawings.

In Fig. 2, the structure of three type of tracks on the magnetic disk incorporated in the present invention are shown, TRKa, TRKb, TRKc. Track TRKa includes data block address information DBA for indicating the position of a data block on the magnetic disk, and error data block information EDB to indicate whether the above mentioned data block contains bad data. Track TRKb also includes data block address information DBA for indicating the position of a data block on the magnetic disk, and alternate data block information ADB to indicate when the above mentioned data block is in use as an alternate data block for a bad data block on track TRKa. Track TRKc is a special data block in which, as is shown in detail in Fig. 1, is recorded each type of information of an address information table AITB. The above mentioned address information table AITB includes a number of written address information area NWAI which indicates the number of individual pieces of information written in the address information table AITB. Also included in the address information table AITB is error data block address information EDBA which indicates the address of a bad data block, alternate data block address information ADBA which indicates the address of a substitute data block used in place of a bad data block, and not in use f lag data NUFD to indicate whether or not a substitute data block is in use.

4 i i i t The number of individual occurances of error data block address information EDBA, alternate data block address information ADBA, and not In use f lag data NUFD in the address information table AITB is shown in the number of written address information area NWAI.

In the following section, the operations carried out by the central processing unit CPU 1 will be described.

(a) Reading process from data block Fig. 3 is a f low chart to explain the read procedure from the data block. If power has been supplied to CPU 1, CPU 1 starts operation. First, in step 1, CPU 1 causes a magnetic head to seek a target data block in track TRKa on the magnetic disk In which the object data block is recorded. In step 2, CPU 1 causes the magnetic head to read data from the data block address information DBA of the above mentioned target data block. In step 3, CPU 1 judges whether the data ID stored in the data block address information DBA is abnormal, that is, bad or not. When the result of judgement is [NO], that is to say, when the afore-mentioned content of data ID is not [BAD], CPU 1 goes to step 4. Then, in step 4, CPU 1 causes the magnetic head to read data f rom the target data block. In step 5, CPU 1 judges whether errors are present or not in the data that has been read. When [NO] is determined as the result of judgement, that is, when a read error is judged to have occured, CPU 1 moves to step 6, and rewrites the data ID of the data block address information DBA to [BAD]. Next, in step 7, CPU 1 adds + 1 to number of written address information area NWAI, and also writes additionally the address of the bad data block in the error data block address information area EDBA, and the address of the alternate data block in the alternate data block address information ADBA, thereby forming address information table AITB. Next, in step 8, CPU 1 sets the corresponding not In use flag data NUFD to [ON]. Next, CPU 1 executes processing for the read error in step 9, and process then terminates. On the other hand, in step 5, when [ NO] is judged, that Is, the data is correctly read, CPU 1 transmits the read data to host computer 7, and finishes all procedures of reading. Afterward, whenever the host computer 7 attempts to read that data block, because the aforementioned content of the data ID is judged t o be [BAD] in step 3, CPU 1 goes directly to step 10 where the address information table AITB is searched. Next, in step 11, CPU 1 judges whether the error data address block information EDBA is present for the target data block or not. Here, when [YES] is judged, that is, when the error data address block information is present, CPU 1 goes to step 12. In step 12, CPU 1 judges whether not in use flag data NUFD is set to [ON] or not. Here, if set to [ON], CPU 1 goes to step 9, and again executes the above-mentioned read error processing. After this, CPU 1 finishes the routine. Thus, it can be seen that the read error processing is repeated only when the ID for the data block address information DBA is set to [BAD]. On the other hand, in step 12, when the not in use flag data NUFD is not set, CPU 1 moves to step 13. In step 13, CPU 1 causes a magnetic head to seek the alternate track, according 6 0 t a to the alternate data block address information ADBA. After this, CPU 1 goes back to step 2 and the above described processes are repeated. Also, in step 11, when CPU 1 judges that the corresponding address is not written in the error data block address information EDBA, the procedure moves to step 14 where CPU 1 recognizes that the objective block has not been detected and CPU 1 completes all procedures.

(b) Writing process to data block Fig. 4 is a f low chart for showing the writing process to the data block. In step 16, CPU 1 causes a magnetic head to seek the target track. In step 17, CPU 1 examines the data block address information DBA for that track. In step 18, when the data ID of the data block address information DBA is [bad], CPU 1 goes to step 19. In step 19, CPU 1 examines the address information table AITB and verifies the number of written address information area NWAI, and searches the error data block address information EDBA and the alternate data block address information ADBA. In step 20, if the corresponding address information from the error data block address information column EDBA is not found, CPU 1 goes to step 24, executes the process for the case when CPU 1 cannot find the target data block, and ends this writing processes. On the other hand, in step 20, if corresponding address information is found, CPU 1 goes to step 21, and in step 21, sets the corresponding not in use flag data column NUFD to [OFF]. Here, [OFF] means that alternate data block is in use. In step 22, according to the corresponding content of the alternate data block address information area ADBA, 7 0 CPUl causes the magnetic head to seek the alternate track. After the execution of step 22, CPU 1 goes back to step 17. In step 17, CPU 1 exceutes the previously described process.

On the other hand, In step 18, when the corresponding data ID of data block address information area DBA Is not [BAD], CPU 1 moves to step 23, and writes data to this track. After excuting step 23, CPU 1 ends all writing processes.

(c) data reading process after writing data one or more times to the alternate data block information ADB If the writing of data to the alternate data block area ADB corresponding to the error data block information EDB is executed one or more times, [ BAD] Is written in the data block address Information DBA on that track, and [ of f] is written in the corresponding not in use flag data column NUFD of address information table AITB. In this state, when host computer 7 tries to read the data from this data block, CPU 1 executes afore- mentioned step 1, step 2, step 3, step 10, step 11, step 12, step 13, step 2, step 3, step 4, step 5 and step 15 shown in Fig. 3. Thus, CPU 1 normally finishes data transfer, accessing the alternate data block information ADB. If In step 5, a new error occurs on this track, as in the above section, (a) reading process from data block, CPU 1 sets the data block address information area DBA in the alternate data block to [BAD], and transfers the desired data from a new alternate block.

While one preferred embodiment of the present invention is described above, it is not intended to limit the present invention by this embodiment.

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Claims

What is claimed is:

1. An apparatus for reading data from and writing data on a data storage device, the apparatus comprising:

(a) judging means for judging whether error data are included in data; (b) writing means for writing, in condition that error data are detected for the first time in said data, an error indicator flag for indicating that error data are detected in the data, and address information for indicating address of substitutive data to replace the error data; (c) writing means for writing correct data, in condition that error data are detected for the first time in said data; (d) reading means for reading the error indicator f lag indicating that error data have been detected in the data, and the address information including the address of the substitutive data; and (e) reading means for reading correct substitutive data, in condition that the error indicator flag indicates that error data have been detected in said data; whereby the error indicator flag, the address information and substitutive data are written when error data are first detected, and the substitutive data block is read without reading the error data block thereafter.

2. An apparatus according to claim 1 wherein a data block is read out from and write down on the data storage 9 device when reading and writing data.

3. An apparatus according to claim 1 which further comprises a contorl means for controlIng operation of the Judging means, writing means and reading means.

4. An apparatus according to claim 1 which further includes a data storage device for storing data.

5. An apparatus according to claim 1 wherein the data storage device is a magnetic disk.

6. An apparatus according to claim 4 wherein the data storage device is a magnetic disk.

7. An apparatus according to claim 5 wherein the magnetic disk is a hard disk.

8. An apparatus according to claim 6 wherein the magnetic disk is a hard disk.

9. A method for reading data from and writing data on a data storage device, the method comprising the steps of:

(a) judging whether error data are included in data; (b) on the condition that error data are detected for the first time In said data, writing an error indicator flag for indicating that error data are detected in the data, and indicating address information for indicating address of substitutive data to replace the error data; (c) writing the correct data, on the condition that error data are detected for the first time in said data; (d) reading the error indicator flag and the address z information on the condition that error data have been detected in the data; and (e) reading correct substitutive data, on the condition that the error indicator flag indicates that error data have been detected in said data; whereby the error indicator flag, the address information and substitutive data are written when error data are f irst detected, and the substitutive data block is read without reading the error data block thereafter.

10. A method according to claim 9 wherein a data block is read out from and write down on the data storage device when reading and writing data.

11. A method according to claim 9 wherein the data storage device is a magnetic disk.

12. An apparatus for reading data and writing data on a data storage device, substantially as herein described with reference to the accompanying drawings.

11 Published 1990 atThe Patent Office, State House, 66171 High Holborn, London WCIR 4TP. Further copies maybe obtamedfrom The PatentOffice. Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent, Con. 1/87