Data processing apparatus and file management method therefor

Details Data processing apparatus and file management method therefor Data processing apparatus and file management method therefor

1999-06-22

2002-04-23

Robertson, David L. (Department: 2187)

Electrical computers and digital processing systems: memory

Addressing combined with specific memory configuration or...

Dynamic-type storage device

C711S112000, C707S793000

Reexamination Certificate

active

06378031

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a data processing apparatus comprising a disk apparatus for recording and reproducing a large amount of continuous multimedia data including digital audiovisual information (herein also maybe referred to as “AV data”) in a personal computer (hereinafter simply referred to as a “PC”) and a home-use multimedia apparatus or the like, and to a file management method therefor.
Conventionally, audiovisual information has been recorded and reproduced mainly on magnetic tape. However, in accordance with the progress in the recent digital technology, a system of recording audiovisual information by using digital signals has become the dominant recording system instead of the recording system using analog signals. On the other hand, the range of uses for recording and reproducing AV data in real time by using the PC is increasing because of the rapid widespread proliferation of the PC and the development and practical utilization of a disk apparatus with built-in mass-storage disk media. In other words, a data processing apparatus including the PC is strongly requested to be able to easily carry out data processing, such as storage, editing and treatment, in accordance with the above-mentioned progress in technology. In the case of the above-mentioned data processing, a file system under the management of a known operating system (hereinafter referred to as an “OS”) installed ordinarily in the PC for example is used as a file management method for the AV data.
A file system included in a typical OS used for the PC is taken here as an example to explain a conventional file management method.
In order to carry out a file management, it is necessary to execute management to find out where a physical position of data recorded in a file is stored on the recording medium (disk medium) of the disk apparatus. On the other hand, the area of the recording medium of the disk apparatus is usually divided into units each referred to as a sector. Continuous logical block addresses (hereinafter each referred to as an “LBA”) are assigned to the individual sectors, so that the disk apparatus deals with its whole area as a single linear area. Therefore, the LBA on the disk apparatus corresponding to the head position of the data, for example, is controlled by the file management in the physical position of data recorded in the file.
Generally, data is divided into a plurality of fixed-length blocks (usually referred to as clusters), and a table indicating the correspondence of each cluster and an LBA on the disk apparatus is used for management. One cluster has a plurality of continuous sectors. The above-mentioned table is referred to as a file allocation table (hereinafter simply referred to as a “FAT”). This FAT holds cluster chain information for linking divided plural clusters to form one file. Furthermore, this FAT is stored and disposed in a recording area different from the data recording area on the disk apparatus. After the PC is started, the FAT is read from the disk apparatus to the main storage apparatus.
The above-mentioned FAT will be described below more specifically referring to FIG.
11
.
FIG. 11
is an explanatory view showing a concrete example of a FAT used for the conventional file management method.
In a conventional data processing apparatus, as shown in
FIG. 11
, a disk medium
100
has a plurality of recording areas, and the AV data and management information for managing the AV data are stored separately in the recording areas respectively corresponding thereto. In other words, the disk medium
100
is provided with recording areas
101
and
102
for storing the FAT and its copy, respectively, as shown in FIG.
11
. Furthermore, the disk medium
100
is provided with a directory management portion
103
for holding plural pieces of file information, a recording area
104
for holding a copy of the directory management portion and a data storage area portion
105
for holding the AV data.
Each cluster of the conventional FAT holds the cluster chain information for indicating the cluster number of the link destination linked to the cluster. By referring to this FAT, clusters can be detected from one cluster to another, whereby it is possible to obtain the record positions of all the data constituting one file. More specifically, when the first cluster number of a file is 2, for example, cluster numbers
4
,
3
,
7
,
6
and
5
can be obtained in sequence in accordance with the cluster chain information as shown in
FIG. 11. A
hexadecimal value “FFFF” shown in
FIG. 11
indicates that the cluster holding this value is the last cluster. Furthermore, values to be stored as the cluster chain information in the FAT are 12-bit, 16-bit or 32-bit data, for example.
When a FAT using 16-bit cluster chain information is explained for example, the maximum value capable of being described as the cluster chain information is (2 raised to the 16th power−1=65,535). In this case, value 0 indicates that the cluster holding this value is a free cluster on the disk medium
100
. Value 65535 (“FFFF” in hexadecimal notation) is used as a special value indicating that the cluster holding this value is the last cluster in the file. As a result, in the case of the FAT using 16-bit cluster chain information, the whole recording area of the disk medium
100
is divided into 65534 clusters and managed. In addition, in the conventional file management method using this FAT, numbers are assigned to clusters, beginning with its head cluster in sequence, to manage the correspondence of the numbers to the LBAs on the disk apparatus. More specifically, each LBA on the disk apparatus can be obtained by (the cluster number corresponding to the LBA)×(the number of sectors per cluster)+(offset LBA). The offset LBA mentioned above is an LBA assigned to the head position of the data storage area portion
105
.
In the conventional data processing apparatus, the file management is carried out by the conventional file management method using the above-mentioned FAT. In the conventional data processing apparatus and the file management method therefor, the FAT is read from the disk apparatus to the main storage apparatus after the apparatus is started. Therefore, in the conventional data processing apparatus and the file management method therefor, when target data is read and/or written on the disk apparatus, the data is read and/or written at high speed referring to the FAT having been read in the main storage apparatus, instead of the FAT on the disk apparatus.
However, the above-mentioned conventional data processing apparatus and file management method therefor cause the following problem. That is to say, in the case of the above-mentioned prior art, the FAT on the disk apparatus is updated after file writing, namely, after file closing. Therefore, if an electric power to the PC or the disk apparatus is shut off during file writing, the FAT on the disk apparatus is not updated. As a result, even if a part of file data at the file writing has been recorded on the disk apparatus before power shut-off, the file management information including the FAT is not updated to that corresponding to the recorded data. This cause a problem of unable to judge which file data corresponds to the data recorded on the disk apparatus, and the file data at the file writing in the power shut-off cannot be read at all.
In order to solve this problem, it may be possible to use a method of frequently updating the FAT on the disk apparatus. However, in the case of this method, both the recording area for holding management information such as the FAT and the recording area for holding data must be accessed frequently and alternatively in the disk apparatus. Particularly when real-time data such as the AV data is recorded while accessing two recording areas alternatively in the disk apparatus, the performance of the real-time processing is impaired fatally. This method is thus not effective.
Furthermore, it may be possible to use a method of coping with

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