JPH06259335A - External storage device - Google Patents

Abstract

PURPOSE:To provide a system which can easily detect and correct an error of a table indicating a data area used for an auxiliary storage device. CONSTITUTION:A read (301) of a 1st table is made and error detection (303) is performed by making a comparison with a value (302) read out of a 2nd table based on the read value; if an error is decided, the 2nd table is retrieved (304, 305, and 406) and when there is a retrieved value, the 1st table is corrected (308), but when not, the 2nd table is corrected (307) to correct the error of the table indicating the data area of the auxiliary storage device.

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 used in an information processing apparatus, and more particularly to error processing of a table of an external storage device which expands a table showing a data storage area in a memory.

[0002]

2. Description of the Related Art External storage having a memory for storing a physical path name indicating a physical position of a file in an external storage device and a logical path name indicating a logical apparent position, and storing each path name. In a device, when a random access memory is used as a memory for storing a path name, a method of adding a parity bit is generally adopted in order to improve reliability of read data. In this method, a parity bit is added to data and written in a memory, a parity check is performed when reading the data from the memory, and when a parity error occurs, an interrupt notifies the control device of the error occurrence. As a result, the control device processes the predetermined interrupt vector.

Further, in order to improve the reliability of the read data, an error check bit is added to the memory for writing, and when the data is read from the memory, the error check bit is used to judge the presence / absence of an error and to determine the bit error. The method of correcting is also commonly used.

As a publicly known example of the external storage device having the above file management, there is JP-A-2-32430.

[0005]

When a memory that stores a physical path name and a logical path name as a table has only a parity check function, the memory data error can be detected, but the error data cannot be corrected. When an error occurs, the table indicating the data area is destroyed, which is a fatal problem for the external storage device.

Further, even in the method of correcting error data by adding an error check bit, correction of one bit or several bits is possible, but correction of all bits is impossible.

An object of the present invention is to reduce the load on hardware in an external storage device having opposing tables,
Moreover, the contents of the table in which the data error has occurred are easily corrected.

[0008]

[Means for Solving the Problems] The contents of the first table are used as addresses, and a second table that stores the addresses of the corresponding first table is stored. The two tables are compared. If they do not match, the two tables are compared. It is determined which is an error, and the table in which the error occurred is rewritten to avoid a data error in the table.

[0009]

By using this method, the table indicating the data area of the auxiliary storage device can avoid a data error on the memory, and a highly reliable auxiliary storage device can be provided. Also,
By reading out the configurations of the two tables and configuring them so as to be optimal for data retrieval at the time of writing, the retrieval of the data area in the auxiliary storage device can be performed at high speed.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the principle of an external storage device using the memory data correction method of the present invention. In FIG. 1, 1 is a memory for a first table and 2 is a memory for a second table. Shows the location of the data set stored in. A control unit 3 reads out the contents of the first table 1 and the second table 2 and performs error detection and error processing. Reference numeral 5 is a local bus in the auxiliary storage device.
Reference numeral 6 denotes an interface section with the host, which is a host bus 7
And exchange commands and data.

FIG. 2 is a diagram showing the relationship between the configuration of the first table 1 and the second table 2 and the data area 4. The data area 4 is divided into sectors each having a plurality of bytes as a unit, and a number is added to each sector in ascending or descending order. Hereinafter, this number is referred to as a physical sector number.
On the other hand, a host accessing the auxiliary storage device reads or writes data by designating a cylinder number, a sector number or the like indicating a data area of the auxiliary storage device.
The cylinder number, sector number, etc. designated by this host are collectively referred to as a logical sector number hereinafter. Here, when the logical sector number designated by the host and the physical sector number indicating the data area in the auxiliary storage device do not have a one-to-one correspondence, for example, the data area is electrically rewritable due to the limited number of rewrites. EEPROM which is a semiconductor memory
When a flash memory is used, the logical sector number and the physical sector number are different because rewriting is performed by averaging over all data areas as a method of relieving the limitation on the number of times of rewriting. Also, the data area can be written only once.
It is obvious that the logical sector number and the physical sector number are different when using the TPROM. Since the logical sector number and the physical sector number are different as described above, the tables for converting the logical sector number and the physical sector number are the first table 1 and the second table 2.

The first table 1 is arranged in ascending or descending order of logical sector numbers and stores physical sector numbers. In FIG. 2, logical sector numbers 1, 2, n, n + 1, n +
The data of 2 are physical sector numbers a, d, k, r,
Indicates that the data is stored in the data area of h. The host reads data from the auxiliary storage device by designating the logical sector number, and the physical sector number in which the data is stored is obtained from the first table 1 based on the designated logical sector number.

The second table 2 is arranged in ascending or descending order of physical sector numbers, and stores logical sector numbers corresponding to the physical sector numbers stored in the first table 1. In FIG. 2, physical sector numbers a, d, h, k, r
In the respective data areas of the logical sector numbers 1, 2, n
This indicates that +2, n, n + 1 data is stored. The writing of data from the host to the auxiliary storage device is also performed by designating the logical sector number, the empty area of the data area of the auxiliary storage device is searched, and the data area to which the data from the host is written is determined. The logical sector number is registered in the second table 2 corresponding to the data area in which the data is written from the host, and the physical sector number in which the data is written is stored in the first table 1 at the position of the logical sector number. register. And the two tables are always matched.

Next, the operation of this embodiment will be described. FIG. 3 is a flow chart of error detection and error processing performed by the control unit 3. When reading data from the host, the control unit 3 reads the physical sector number from the first table 1 based on the logical sector number designated by the host (301). A logical sector number is read from the second table 2 using the read physical sector number (302). If the logical sector number designated by the host and the logical sector number read from the second table 2 match, the values in the first and second tables are normal. However, if they do not match, it can be determined that either the first or second management table has an incorrect value (303), and error correction processing is performed. First, assuming that the first table 1 is broken, the corresponding logical sector number is searched from the second table 2 (30
4,305,306). If the corresponding logical sector number is found from the second table 2 (305), it means that the contents of the first table 1 are corrupted as assumed,
The first table 1 is rewritten (308). However, when the corresponding logical sector number is not found in the entire area of the second table 2 (306), it is clear that the values of the first table 1 are normal, and the contents of the first table 1 are The contents of the second table 2 indicated by the physical sector number are rewritten (307). As a result, even if the contents of the first table 1 or the second table 2 are corrupted, they can be completely corrected.

Further, the reliability can be further improved by adding a parity bit to the first table 1 or the second table 2 or both tables to provide a parity check function. For example, when the first table 1 has a parity error, it can be easily determined that the physical sector number read from the first table 1 is broken, the second table 2 is read, and the normal physical sector number is read. Ask. By writing this normal physical sector number in the first table 1, the broken first table 1 can be corrected. On the other hand, when the second table 2 has a parity error, it can be easily determined that the logical sector number read from the second table 2 is broken, and the logical sector number designated by the host is used as the second table 2 It is possible to correct by writing in the corresponding area of.

[0017]

As described above, according to the present invention, it is possible to correct the error in the table showing the data area of the auxiliary storage device by the above processing, and to provide a highly reliable auxiliary storage device.

[Brief description of drawings]

FIG. 1 is a block diagram of an external storage device using a memory data correction method of the present invention.

FIG. 2 is a diagram showing a relationship between two tables and a data area.

FIG. 3 is a flow chart of a memory data correction method of the present invention.

[Explanation of symbols]

1 ... 1st table, 2 ... 2nd table, 3 ... control part, 4 ... data storage area, 5 ... local bus, 6 ... host interface part, 7 ... host bus.

Claims (1)

[Claims] 1. Setting means for setting a physical path representing a physical position of data in an external storage device for a logical path name representing a logical position of data, and a first means for storing the logical path name. In an external storage device comprising one storage means and second storage means for storing the physical path name, comparison means for comparing the first storage means and the second storage means, and the comparison And a correction means for correcting the first or second storage means from the search result of the search means when the results differ from each other. And an external storage device.