KR100704621B1 - Method and apparatus for guaranteeing data integrity of portable storage device - Google Patents

Abstract

The present invention relates to a method and apparatus for ensuring data integrity of removable storage devices.

According to an embodiment of the present invention, a method of guaranteeing data integrity of a mobile storage device may include receiving a request for a file operation from an application or an operating system, generating information on the requested file operation, and logging the information. Storing in a file and performing a file operation according to the stored operation information.

File System, File Allocation Table (FAT), Block Map, Data Block, Integrity

Description

Method and apparatus for guaranteeing data integrity of portable storage device

1 is a block diagram illustrating a configuration of a conventional file system and a storage medium.

2 is a conceptual diagram illustrating storage of a file through a block map in a conventional file system.

3 is a block diagram illustrating occurrence of an error when deleting a file in a conventional file system.

4 illustrates a configuration of a file system and a storage device according to an embodiment of the present invention.

5 is a conceptual diagram illustrating an embodiment of a log file according to an embodiment of the present invention.

6 is a block diagram illustrating a process of recovering an error when deleting a file according to an exemplary embodiment of the present invention.

7 is a block diagram illustrating a process of recovering an error when generating a file according to another exemplary embodiment of the present invention.

8 is a flowchart illustrating a process of file operation and error recovery according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

10: file system 50: log manager

100: block map 150: log files

200: data block

The present invention relates to a method and apparatus for efficient data management of a file.

A file is a collection or collection of data stored in a hard disk, memory card, CD-ROM, or the like. Files serve a variety of functions, such as providing information to a system such as a computer, PDA, or mobile phone, running a function, or providing information to a user.

The file system provides methods and functions for writing, reading, and using files. Digital devices such as computers include FAT (File Allocation Table), NTFS (New Technology File System), HPFS (High Performance File System), and the like. The file system performs functions for efficient file management, and provides fast data retrieval, recovery, and large data support. The file system is focused on improving the performance of the entire system by smoothing file processing while reducing bottlenecks caused by storage media having a relatively slow processing speed compared to processors such as CPUs. On the other hand, many digital devices dealing with digital multimedia use a file system compatible with the computer to enable file exchange through the computer. Thus, many digital devices currently use a file system to store multimedia data.

As the multimedia data and digital devices increase, the demand for portable storage devices increases. In the past, removable storage devices were floppy diskettes, but recently, various removable storage devices such as USB memory, MMC cards, SD cards, and memory sticks are easily released. Along with this flow, some problems are also raised in file management of removable storage devices.

Before looking at these problems, the general structure of the current file system is as follows.

1 is a block diagram illustrating a configuration of a conventional file system and a storage medium. File systems such as FAT, HPFS, and NTFS manage files through block maps. As shown in FIG. 1A, a hard disk or a memory card is roughly divided into a data block and a block map.

The data block may be one unit for storing data and may be one unit for storing data in the storage space. It becomes a unit for storing data, such as 512 bytes or 1024 bytes, and larger data is stored in pieces according to the size of the storage unit. In a file system using FAT, such data blocks are called clusters.

A block map is a collection of information about the data block. Therefore, as can be seen in (a), the block map 100 and the data block 200 may be stored in the storage device. In addition, the file system 10 exists to manage the mapping and the file between the block map 100 and the data block 200.

The structure of the block map and data block is shown in (b). Each of the blocks 101 and 102 constituting the block map shows the state of the corresponding data block. That is, it has information indicating whether a file is stored in the data block or whether the data block can be stored. In the FAT system, a file allocation table is an example of a block map. When the information on the blocks constituting the block map is reviewed, the state of the data block can be known without directly examining the entire data block. A value of a block of the block map indicates a position of the next data or indicates that data is not stored in the corresponding data block. It can also indicate if the data block, for example, the cluster, is damaged so that it can't store the file. The block map will be described with an address from 1 for convenience, which is only one embodiment of the file system implementation. The block map of address 1 shows information about the data block of address 1.

Table 1 shows the values indicated by the blocks in the block map in the FAT system.

FAT12 FAT16 FAT32 Mark available 000 0000 00000000 Show reserved cluster 001 0001 00000001 User data 002-FF6 0002-FFF6 00000002-0FFFFFF6 Bad Cluster FF7 FFF7 0FFFFFF7 End mark FF8-FFF FFF8-FFFF 0FFFFFF8-0FFFFFFF

The value indicated by the block may vary depending on the implementation of the system. Other file systems, such as NTFS or HPFS, display values according to the promised definition of the file system.

However, these data may not always be stored sequentially. Storage space that can be used while files are deleted and stored may be scattered throughout the storage medium. The block map organizes the positions of the blocks into a linked list so that data can be read sequentially from several data blocks forming one file. This connection is made through blocks in the block map.

Hereinafter, in the present specification, a block constituting the block map is called a mapping block.

2 is a conceptual diagram illustrating storage of a file through a block map in a conventional file system. As described above, the block map has information about a data block that is a storage unit of the data area. The data block may vary depending on the file system such as 512 byte or 1024 byte.

Looking at how file.txt is stored, file.txt points to the beginning of the mapping block that shows the information of the data block that starts. The inside of the block map forms a link by sequentially connecting the mapping blocks representing the data blocks in which the file is stored. You can see that file.txt is stored in a data block called 3. Therefore, to read the data in this file, you need to refer to the mapping block at address 3. For convenience of explanation, blockmap (k) means a mapping block of k addresses, and datablock (k) means a data block of k addresses.

blockmap (3) has 0004, which means that the next data constituting this file is stored in address 4, namely datablock (4). Information about the data block of address 4 is stored in the mapping block of address 4. Blockmap (4) has a value of 0006, which shows that the next data is stored in data block 6. In this way, the block map can sequentially read the data constituting the file. In the example of FIG. 2, file.txt shows that data blocks are sequentially stored in data blocks 3, 4, 6, 7, and 8 through the connection of mapping blocks. The value of blockmap (8) is 0xffff, which means the end of the file. A value other than 0xffff may be promised to indicate the end of the file. However, to avoid confusion, it should be a value that does not overlap with the address of the mapping block. For example, if there is a mapping block addressed to 0xffff, you will have confusion, so you will have to use a larger value or a different value that does not overlap.

When using a file system based on a block map, there is an advantage that data can be stored by providing a logical connection even when not physically connected. However, a problem may occur when deleting or moving a file. These problems will be discussed with reference to FIG. 3.

3 is a block diagram illustrating occurrence of an error when deleting a file in a conventional file system.

3 illustrates a process of deleting file.txt of FIG. 2. file.txt consists of five data blocks. To delete a file, the mapping block corresponding to five data blocks must be set to zero. After this zero deletion process, file.txt must be deleted from the file system. If file.txt in the file system is not deleted, the data is deleted from the block map, but file.txt exists in the file system, which compromises the integrity of the data. FIG. 3 shows a case in which a task related to deleting a file has been performed in the block map but the file still exists in the file system.

In fixed storage devices, integrity is provided by verifying after deleting or moving files. However, in the case of a portable storage device, it is difficult to provide data integrity. If a removable storage device is easily removed during a file operation, it is because only a portion of the file operation exists. In addition, in the case of a portable digital device that uses a lot of removable storage devices, since the power is supplied through the battery, when the power goes out during the file operation, a part of the file operation may also exist.

In the past, there has been a patent (Korean Patent Application Laid-Open No. 2000-0057005) for providing the integrity of the file. The invention has two external files in the file system and holds information about the file system. However, it contains information about the length and data type of the file and modifies the two files after the file is updated. It is a method to maintain file system integrity through two files to maintain consistency, but it provides a function to correct errors accumulated in the file system rather than errors in file operations.

Therefore, there is a need for a method of guaranteeing the integrity of a file even if a removable storage device or a power problem occurs during file operation.

An object of the present invention is to ensure the data integrity of a removable storage device.

Another object of the present invention is to recover from errors occurring during file operations of a removable storage device.

The objects of the present invention are not limited to the above-mentioned objects, and other objects that are not mentioned will be clearly understood by those skilled in the art from the following description.

The present invention relates to a method and apparatus for ensuring data integrity of removable storage devices.

According to an embodiment of the present invention, a method of guaranteeing data integrity of a mobile storage device may include receiving a request for a file operation from an application or an operating system, generating information on the requested file operation, and logging the information. Storing in a file and performing a file operation according to the stored operation information.

According to another aspect of the present invention, there is provided a method of guaranteeing data integrity of a removable storage device, the method including receiving a command for requesting to drive a file system, and a log file for a recent file operation through a log manager present in the file system. Reviewing the information and comparing the information with the information of the files in the storage device, and if the recent file operation of the log file is not completed, performing a file operation according to the information.

An apparatus for guaranteeing data integrity according to an embodiment of the present invention includes a file system that receives a request for a file operation from an application or an operating system, a data block storing data of a file, and a mapping block storing information about the data block. And a log manager for storing file operation information in the log file and comparing the operation information with the data block and the block map.

The terms used in the present specification are summarized as follows.

The storage media that make up a computer consist of a file system and the data that is actually stored. As described above, the file system refers to a system for efficiently managing files. The following is a brief overview of the file systems used in many systems.

FAT (File Allocation Table)

FAT is a file system supported by the Windows system and exists on the disk in the form of a file table. There are two FATs to recover from a FAT corruption. This is the simplest form of file system supported by Windows NT. FAT is an early file system, and now FAT12, FAT16, FAT32, etc. are appearing. FAT16 can be used in other operating systems besides the Windows operating system.

HPFS (High Performance File System)

Introduced in OS / 2 1.2, the file system includes a directory structure in FAT, but includes automatic sorting based on file names. It increases the flexibility of the Naming convention and reduces the disk loss by making the unit of file allocation the physical sector in the cluster. HPFS increases speed by allowing a file to be stored in a series of connected sectors.

NTFS (New Technology File System)

NTFS manages files as directories and allows sorting like HPFS. It also provides the ability to recover from file system errors and prevent sector deletion. Review what has been done to the file and cancel it to ensure consistency within the file system. It is mainly used in Windows NT, and is also used in Linux.

File operations

The action taken on a file in the file system. Operations that require changes to data include creating and deleting directories and files, deleting and truncating, renaming files and directories, adding data, merging files, and changing file / directory properties. A directory is a file that stores information about other files. A directory can be viewed as a file that stores names, starting data block map information, and other information about other files or directories.

This file system applies to digital devices that store data in addition to computers. Therefore, the file system can be applied to devices that handle digital data such as mobile phones, PDAs, notebook computers, and digital TVs. The file system can also be applied to removable storage devices such as floppy disks, flash memory, memory stick duo, or SD card or MMC (MultiMedia Card) memory.

File systems have their own characteristics. The structure of most file systems including the file systems listed above is shown in FIG. A block map that contains information about the location of each file, and a collection of data (bits) that make up these files.

4 illustrates a configuration of a file system and a storage device according to an embodiment of the present invention.

The term '~ part' used in this embodiment, that is, '~ module' means a hardware component such as software, FPGA or ASIC, and the module performs certain functions. However, modules are not meant to be limited to software or hardware. The module may be configured to be in an addressable storage medium and may be configured to play one or more processors. Thus, as an example, a module may include components such as software components, object-oriented software components, class components, and task components, and processes, functions, properties, procedures, subroutines. , Segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functionality provided within the components and modules may be combined into a smaller number of components and modules or further separated into additional components and modules. In addition, the components and modules may be implemented to play one or more CPUs in a device or secure multimedia card.

The log system 50 exists in the file system 10. The log manager reads the information recorded in the storage device when the system starts up and completes the operation of the incomplete file system when the file system loses power or the removable storage device is abnormally terminated.

The log file may occupy a portion of the actual data storage device 500 or may be implemented inside the file system. 4 shows an example of occupying a part of the data storage device 500.

The log file records information about operations performed on the file. Description of information to be recorded is given in FIG. 5. After recording information about the operation in the log file, the file system performs the actual file operation. The file operation can modify only the block map or both the block map and the data block.

5 is a conceptual diagram illustrating an embodiment of a log file according to an embodiment of the present invention. The log file 150 may include information related to file operations. The log file 150 may exist together with the log manager in the file system as described above, or may be stored in the form of a file in the data storage device. The log file 150 includes a serial number 151, a type of operation 152, an associated mapping block address 153, operation related information 154, and operation result 155.

The serial number 151 becomes an identifier for storing file operation information. The size of the storage space occupied by the log file depends on the size of the data storage device. Therefore, a certain number of file operation information may be stored, and when a file operation error occurs, the file operation may be performed again by referring to the most recent file operation information.

The operation type 152 is a part which informs what operation was performed. In FIG. 5, in one embodiment, lowercase letters indicate operations performed on files and uppercase letters. n, d, and m denotes the creation, deletion, and movement of files, respectively, and N, D, and M denotes the creation, deletion, and movement of directories, respectively. Although not shown in FIG. 5, a or A may be performed to add data. The information about the type of file operation may be briefly processed as one character, and may be stored in a structure including more detailed information.

The mapping block address 153 stores a start mapping block of a file on which the file operation is to be performed. You can examine what data is in this mapping block to see if the file operation is complete.

The operation related information 154 includes information required for operation. When a file or directory is created or deleted, the name of the file or directory may be stored. When a file or directory is moved, the file or directory may include information about a directory to which the file or directory is to be moved. This may vary for each implementation and file system.

The operation result 155 is information about whether to perform the file operation. However, one embodiment of the present invention does not store the execution result for all file operations. This is because storing the results of many file operations individually causes file system overhead. Therefore, it is not a way to always save the execution result after the file operation occurs, and the file operation of the log file exists as it is. The change of the execution result will be described later.

After the file operation K is completed and no other file operation occurs, information about the K file operation remains in the log file. Then, if the removable storage device is removed and then rejoined, the file system first examines the log file. The information on the most recent file operation stored in the log file (information on the file operation K) and the structure of the block map and the data block are reviewed to see if the K operation is successful. As a result, if K operation is not successful, K operation is performed again. If there is a block map and data block matching the result of K operation, another operation is performed later.

In this process, if the K operation is not performed successfully and the K operation is performed again, the aforementioned operation result 155 may be set to 1 after the operation is completed. Alternatively, if it is difficult to perform the K operation again, the operation result 155 may be set to 2 so as not to perform the K operation again, and to process the work that was not present. Since the operation result 155 is not modified for every file operation, the overhead of generating a log file can be reduced. Only in certain cases is it possible to store the results of the work in operation result 155, thereby avoiding excessive comparison review at the start of the file system.

6 is a block diagram illustrating a process of recovering an error when deleting a file according to an exemplary embodiment of the present invention.

The file system stores information related to the delete operation in the log file 150 for file deletion. As you can see in (a), the file to delete is file.txt, which is linked in the order of mapping blocks 3, 4, 6, 7, and 8. To delete a file, delete the part referring to file.txt in the file system, and modify the mapping blocks 3, 4, 6, 7, and 8 assigned to file.txt to be reusable. In an embodiment of the present invention, in order to reuse the mapping block, a method of modifying the value of the mapping block to 0 is intended.

(b) shows the result of modifying the mapping block. The values of the mapping blocks 3, 4, 6, 7, and 8 are zero and can now be used by other files or directories. However, the information about file.txt in the file system has not been deleted yet. After modifying the mapping block, before deleting file.txt from the file system, the removable storage device may be removed or powered off. In this case, the modification of the mapping block is completed, but the file system remains intact, and the integrity is not satisfied.

However, since information related to deletion exists in the log file 150, rework is possible when the removable storage device is coupled or attached to the system or powered on.

The file system examines the log file 150 when the removable storage device and the digital device are combined or powered up. Examine the log information related to recent file operations to see if work was performed on this log. In FIG. 6, the log stored in the log file indicates that the start mapping block address of file.txt is 3 and the delete (d) operation is performed. Based on this information, the file system removes file.txt if it exists. Since the mapping block at address 3 is zero, no modification is necessary for the mapping block, so the file system does the following:

Here, the operation result 155 may be modified. This may vary depending on the implementation of the file system or the circumstances of the system, where the results can be saved after the re-execution of an incomplete file operation, or in the case of a file operation that is difficult to re-execute. Can be. Also, in order to prevent frequent comparison and review, the operation result 155 of the log information may be set to be completed after rerunning.

7 is a block diagram illustrating a process of recovering an error when generating a file according to another exemplary embodiment of the present invention.

The file system allocates a start mapping block to store the new file. Before creating this file, save the information to record that you've created newfile.txt in the log file. When creating a file, the address of the mapping block may not be stored. It stores file creation information in the file system, finds an available mapping block, and maintains information about the mapping block (such as an address) and file name in the file system.

First, we store information about file operations in a log file. The operation type 152 may be set to n, which means generation of a file, and the associated mapping block address 153 may be set to 0 or blank. This may vary depending on the implementation of the file system. If the address of the starting mapping block of the file is known before the file is created, the address of the corresponding mapping block may be set. The operation related information 154 includes a file name to be generated.

After storing the information related to file creation in the log file, perform the work related to file creation in the file system as shown in (a). Create newfile.txt and search the block map to enter the address of the available mapping block. If power goes out or the removable storage device is removed during this process, a file (newfile.txt) exists in the file system without a mapping block.

However, when removable storage devices are combined or powered up again, the file system examines the log file and compares the file structure of a recent storage operation with the actual storage device's file structure. As a result, the file system knows that the creation of newfile.txt is not complete and does the rest. As a result, 5 mapping blocks are allocated to newfile.txt as shown in (b).

6 and 7 store information about an operation before a file operation according to an embodiment of the present invention. The information to be stored may vary depending on the file system and the nature of the operation, which may be different from the information items constituting the log file shown in FIG. The log file shown in FIG. 5 corresponds to an embodiment for implementing the present invention, but is not limited thereto. For example, when a directory is moved, information about a parent directory before the movement of the directory and a parent directory after the movement may also be included. It can also contain information about the files that exist in the directory to be moved.

8 is a flowchart illustrating a process of file operation and error recovery according to an embodiment of the present invention.

(a) shows the operations performed by the file system when performing operations related to files. First, a command for file operation is received from an operating system or another application (S102). In order to store information about the operation in a log file, operation information must be generated (S104). Examples of operation information to be generated may be the items of FIG. 5.

In operation S106, information about an operation to be performed is stored in a log file. This can be done by a log manager within the file system. After storing in the log file, the file system performs the file operation (S108).

(b) shows the operation when the power supply is cut off or the portable storage device is combined with the digital device.

 When the power is supplied or when the portable storage device and the digital device are combined, the file system starts (S110). The file system may be requested to drive from a digital device or may be started by an application in a removable storage device. The log manager in the file system reviews the log file (S112). A review can be obtained by examining the contents of the log file and the file status of the storage device. The result of the operation contents recorded in the log file is compared and examined in the block map or the data block (S114). If present, the operation is successful and waits for another operation (S118). If it does not exist or the result is different from each other, the operation can be performed again to maintain integrity (S116). If there is a problem in performing the operation, the operation result can be modified so that the operation information of the log file is no longer executed.

Those skilled in the art will appreciate that the present invention can be embodied in other specific forms without changing the technical spirit or essential features of the present invention. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive. The scope of the present invention is indicated by the scope of the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and the equivalent concept are included in the scope of the present invention. Should be interpreted.

By implementing the present invention it is possible to ensure the integrity of the data stored in the removable storage device.

By implementing the present invention, it is possible to recover from errors occurring during file operations of removable storage devices.

Claims (23)

Receiving a request for file operation from an application or an operating system; Generating, by a file system, information about the requested file operation; Storing the generated information in a log file through a log manager residing in the file system; And And performing a file operation according to the stored operation information. The method of claim 1, And the file comprises a directory. The method of claim 1, Wherein the information includes a portion of information about a file structure of the removable storage device when the operation is complete. The method of claim 1, Wherein the information includes information needed to re-perform the operation if the operation is not completed. The method of claim 1, And the performing step does not store the result of the file operation in a log file after performing the file operation. delete The method of claim 1, The file operation may be any one of a file deleting operation, a generating operation, an operation of adding a content, a moving operation, a copying operation, or a merging operation. Receiving a command for requesting to start the file system; Reviewing information on a recent file operation of a log file through a log manager existing in the file system; And Comparing the information about the reviewed file operation with information of files in a storage device; If the latest file operation of the log file is not completed based on the comparison result, re-performing the file operation according to the information about the reviewed file operation. The method of claim 8, And the file comprises a directory. The method of claim 8, Wherein the information includes a portion of information about a file structure of the removable storage device when the operation is complete. The method of claim 8, Wherein the information includes information needed to re-perform the operation if the operation is not completed. delete The method of claim 8, The file operation may be any one of a file deleting operation, a generating operation, an operation of adding a content, a moving operation, a copying operation, or a merging operation. The method of claim 8, The log file includes a serial number, information on a type of file operation, and a result of the file operation. The method of claim 8, After the step of performing the file operation again, And setting a flag indicating that the information on the latest file operation has been performed again. A file system that receives a request for a file operation from an application or an operating system and generates information about the received file operation; A data block in which data of the file is stored; A block map that is a set of mapping blocks that store information about the data block; A log file which is a set of information on the generated file operation; And And a log manager for storing file operation information in the log file and comparing the operation information with a data block and a block map. The method of claim 16, And the mapping block has information about a data block in which data of the file is stored. The method of claim 16, And the file includes a directory. The method of claim 16, The file operation information stored in the log file includes a part of information on the file structure of the removable storage device when the operation is completed. The method of claim 16, And the information includes information necessary to re-perform the operation if the operation is not completed. The method of claim 20, And the information includes information indicating completion of the operation after performing the operation again when the operation is not completed. The method of claim 16, And the file operation is any one of a file deleting operation, a generating operation, an adding operation, a moving operation, a copying operation, and a merging operation. The method of claim 16, And the log file includes a serial number, information on the type of file operation, and a result of the file operation.

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