JP3178671B2 - File system and its file recovery method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a file system in a file structure such as UNIX and a file recovery method thereof.

[0002]

2. Description of the Related Art Conventionally, a UNIX system has a simple tree structure without a closed file structure, a file is a simple character string, very easy to access, and a file is specified in the same manner as an input / output device. It consists of a syntax and has various programming languages and editing programs due to its extensibility.

As a file recovery method for such a UNIX system, a method as shown in FIG. 5 is known.
This conventional file system includes a process 1 as an application program, an external storage device 2, a file access unit 11, and a file restoration process 21.

A conventional file system having such a configuration operates as follows according to a flowchart shown in FIG. 6 and a specific flowchart shown in FIG. That is, first, when the application is started from the process 1, the application of the file restoration process 21 operates (step C1), the restoration program of the file 7 in the external storage device 2 is started, and the file restoration process is performed before the external storage device 2 is used. 21 refers to the update log 3 and repairs all files that need to be repaired. And file 7
When the directory 8 and the update log 3 match, the file management block 4 recognizes the end of the restoration and ends the restoration. Therefore, / tmp / test can be deleted. Thereafter, the use of the application of the process 1 starts (step C2), and / tmp / t is stored in the external storage device 2.
est is accessed (step C3), and the application of process 1 is terminated.

[0005]

However, according to this conventional technique, all the files that need to be repaired are repaired before the external storage device 2 is used, so that it takes time to actually start the application. However, there is a problem that it takes time until the external storage device 2 can be used at the same time.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a file recovery method in a file system that can start an application and access an external storage device at high speed.

[0007]

According to the present invention, there is provided a file system for managing files and directories in an external storage device, recording an update record of a file in an update log, and restoring the file from the update log. Backing up the update log in the external storage device
A hash table that stores updated file information according to a hash function based on the update log ,
When the application is started, the file is restored with reference to the hash table.

[0008] In the above file system, the external storage device, and a file management block for managing files for each file and directory that indicates a file, the file Toosa are indicators to the directory
Characterized by comprising the al.

In the above-mentioned file system, there is provided a process for starting an application to operate the file, and a file management means for directly acting on the external storage device under the instruction of the process. A file access unit that uses the external storage device according to the application; a file repair unit that repairs the file; and a hash table creation unit that creates the hash table.

The present invention also provides a file recovery method for a file system which manages files and directories in an external storage device, records an update record of a file in an update log, and recovers the file from the update log. In the above, by using the external storage device ,
Starting a file repair, creating a backup update log that is a backup of the update log, creating a hash table according to the updated content of the backup update log, and Retrieving the hash table upon access to the file, checking whether the file needs to be repaired, and repairing the file if the file needs to be repaired. Accessing the file.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments according to the present invention will be described.
This will be described in detail with reference to the drawings.

[First Embodiment] (Configuration of this Embodiment) Referring to FIG. 1, a file system of this embodiment comprises a process 1 for accessing a file, an external storage device 2, a file management means 11, It is composed of Here, no file repair process is necessary.

The external storage device 2 includes an update log 3, a backup update log 4, a hash table 5, a file management block 6, a file 7, and a directory 8. The external storage device is a storage device that stores programs and data in an accessible state, and corresponds to a hard disk, a floppy disk, a magnetic tape, or the like.
The update log 3 is a record of the update operation of the file 7, the backup update log 4 is a storage area for backup of the update log 3, and the hash table 5 stores a directory of a file for repair according to a hash function. The file management block 6 is an area that manages files for each file, the directory 8 is a table in which the names of the files and information related thereto are summarized, and the file 7 stores the files for each file. Area.

The file management means 11 includes a file access means 12, a file restoration means 13, and a hash table creation means 14. The file access unit 12 is a unit that accesses the file 7 in accordance with the application program of the process 1. The file restoration unit 13 is a hardware unit that includes a program that operates on the external storage device 2 when the file 7 is restored. The hash table creating means 14 is a part for forming a table according to a hash function at a predetermined time.

The hash table 5 is shown in FIG.
And will be described. The hash table 5 calculates the remainder of the file log by dividing the file name by 64 and digitizing the file name.
Connect logs to an interactive list. FIG. 2 shows an example in which the log of the file A, the log of the file B, and the log of the file X are recorded in the column of remainder 0, and the log of the file C is recorded in the column of remainder 2. For example, if there is a log with a file name of FFFF, F = 15, the total is 60, and if it is divided by 64, the remainder will be 60. Therefore, the log of FFFF is recorded as a table in the column of the remainder 60. Then, in the search stage, when trying to search the log file of FFFF, it is sufficient to search the remaining 60 columns, so that the effect of the hash function that the log can be easily searched can be exhibited.

The above-mentioned means and blocks function and operate as follows.

The file access means 12 refers to the file management block 6 in the external storage device 2 and controls access to the file 7 and the directory 8.

The file repair means 13 repairs the file 7 which needs to be repaired. The hash table creation means 14 obtains information on the file 7 that needs to be repaired from the update log 3, quantifies the file name, arranges, for example, the remainder of the number divided by 64 as a table index, and sets the hash table 5 Create

To further explain the present embodiment conceptually, in FIG. 1, the file system includes a backup update log 4 in addition to the update log 3 in the external storage device 2.
And a hash table 5. External storage device 2
Is started, the update log 3 is copied to the backup update log 4, and the updated contents are registered in the hash table 5 from the backup update log 4. Thereafter, when the file 7 is accessed, the hash table 5 is searched first, and if the file 7 is to be repaired, the file 7 is repaired and then the file 7 is accessed.

In this manner, the restoration process before using the external storage device 2 is omitted, and the restoration can be performed while accessing the file.

(Operation of the Present Embodiment) Next, FIGS.
The overall operation of the present embodiment will be described in detail with reference to the flowchart of FIG.

In FIG. 1, this file system has a backup update log 4 and a hash table 5 in addition to the update log 3 in the external storage device 2. When the use of the external storage device 2 is started, the update log 3 is copied to the backup update log 4, and the updated contents are registered in the hash table 5 from the backup update log 4. Thereafter, when the file 7 is accessed, the hash table 5 is searched first, and if the file 7 is to be repaired, the file 7 is repaired and then the file 7 is accessed.

In this manner, the restoration process before using the external storage device is omitted, and the restoration can be performed while accessing the file.

Referring to FIG. 3, first, process 1
Starts the operation of the application, and when the use of the external storage device 2 is started via the file access means 12, a backup update log 4 which is a backup of the update log 3 is created (step A1 in FIG. 3). Next, a hash table 5 is created from the backup update log 4 (step A2).

Further, when the file 7 is accessed from the process 1, the hash table 5 is searched (step B1), and it is checked whether the file needs to be repaired. Is performed (step B2), and file access is performed (step B3).

Next, a description will be given using a specific example.

As shown in FIG. 4, when a directory is indicated by a / symbol and a file called / tmp / test is deleted, the / tmp directory and the file management block 6 corresponding to / tmp / test are updated. At this time, the fact that these pieces of information are updated is described in the update log 3 in advance. When the system is restarted with only the update log 3 described, the update log 3 is backed up to the backup update log 4.
And a hash table 5 is created. In the hash table 5, there is a record that / tmp / test was being deleted. Next, when there is access to / tmp / test, the hash table 5 is accessed (step B1), and / tmp / tes
t indicates that it was being deleted (step B
2) After deleting / tmp / test from the file 7 (step B3), the file access to / tmp / test is an access in a state where there is no file.

In this way, if processing such as file update (deletion, addition, change), generation, and reorganization and corresponding directories are created in the hash table 5 as a table, the necessity of recovery of the update or the like becomes necessary. Therefore, even if the work is interrupted halfway during recovery or the same file is searched by searching the hash table 5 when the work is resumed, the file is searched after the file is recovered. Therefore, the latest file is used, and the situation of erroneous search can be prevented.

[0029]

According to the present invention, instead of restoring all files that need to be restored before starting use, a hash table for searching for an object to be restored before starting use is created. The time required to start using the external storage device can be greatly reduced.

In the hash table, even if there are thousands of update logs, necessary update logs can be searched at high speed by digitizing the file names, and as a result, the use start time can be shortened.

[Brief description of the drawings]

FIG. 1 is a system diagram of a file recovery method according to the present invention.

FIG. 2 is an exemplary diagram of a hash table used in a file recovery method according to the present invention.

FIG. 3 is a flowchart of a file recovery method according to the present invention.

FIG. 4 is a specific flowchart of the file recovery method of the present invention.

FIG. 5 is a system diagram of a conventional file recovery method.

FIG. 6 is a flowchart of a conventional file recovery method.

FIG. 7 is a specific flowchart of a conventional file recovery method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Process 2 External storage device 3 Update log 4 Backup update log 5 Hash table 6 File management block 7 File 8 Directory 11 File management means 12 File access means 13 File repair means 14 Hash table creation means 21 File repair process

Claims (6)

(57) [Claims] 1. A file system for managing files and directories in an external storage device, recording an update record of a file in an update log, and restoring a file from the update log, wherein: Back up the update log
File information updated based on the backup update log
A file system, comprising: a hash table for storing information according to a hash function; and restoring the file by referring to the hash table when an application is started. 2. A file system according to claim 1, to the external storage device, and a file management block for managing files for each file and directory which indicates the file, and the file to be indexed in the directory
A file system further provided. 3. The file system according to claim 1, further comprising: a process for starting an application to operate the file; and a file management unit that directly operates on the external storage device under instructions of the process. The file management means includes a file access means using the external storage device according to the application, a file restoration means for executing the restoration of the file, and a hash table creation means for creating the hash table. And file system. 4. A file recovery method for a file system, which manages files and directories in an external storage device, records an update record of a file in an update log, and recovers the file from the update log. By using storage , you can repair files.
Starting a recovery, creating a backup update log that is a backup of the update log, creating a hash table according to the updated content of the backup update log, and Searching for the hash table when there is access, checking whether the file needs to be repaired, and repairing the file if the file needs to be repaired. Accessing a file. 5. The file recovery method for a file system according to claim 4, wherein the step of accessing is performed by a file access unit between the process and the external storage device. A file recovery method for a file system. 6. The file recovery method for a file system according to claim 4, wherein the hash table comprises a table obtained by digitizing a file name of the backup update log, dividing the file name by a predetermined value, and following the remainder. Characterized file recovery method of file system.