Data processing: database and file management or data structures – Database design – Data structure types
Reexamination Certificate
1997-10-23
2003-05-13
Choules, Jack (Department: 2177)
Data processing: database and file management or data structures
Database design
Data structure types
C707S793000, C707S793000, C711S150000, C711S161000, C711S162000
Reexamination Certificate
active
06564231
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for managing files in a library including a plurality of recording media that record data as files. Further, the invention relates to a server device for library which is provided with a library including a plurality of recording media that record data as files, and distributes the data to a plurality of terminal units connected through a network.
BACKGROUND OF THE INVENTION
In computers of late years, processing speed is higher, and spread of mass storage devices increases the amount of data that can be handled. As a device for storing mass data including character information, audio, moving pictures and the like, and regenerating or playing back the data according to requests of a plurality of terminal units, a server for library has received attention. Generally, file servers distribute data to a plurality of terminals through a network. Among such file servers, a server for library has a library including a plurality of recording media that are relatively low-priced and of large capacity, such as optical disks, as a main storage device, and has been expected in uses for handling mass data, such as multimedia.
A description is given of a conventional server for library that handles moving picture data.
FIG. 27
is a diagram illustrating a conventional network system having a library. Reference numeral
1
designates a library, and the library
1
keeps many disks, such as optical disks, as recording media that record data. Reference numerals
2
to
6
designate disks that record data, and the recorded data are treated as files. Reference numeral
11
designates a disk storage unit that stores the disks. Reference numerals
12
to
15
designate drives for inserting the disks and performing record and playback. Reference numeral
16
designates an arm for inserting/removing the disks into/from the disk storage unit
11
and the drives
12
to
15
and conveying the disks. Reference numeral
17
designates an arm control unit for controlling the operation of the arm
16
. Reference numeral
18
designates a bus for transferring data of the disks that are inserted into the drives
12
to
15
and transferring control data to the arm control unit
17
. Reference numeral
19
designates a server for library utilizing a personal computer or a work station. Reference numeral
20
designates a hard disk that records contents of the disks in the library
1
, records of requests from terminal units, playback request frequency information on the basis of the request records and the like. This hard disk
20
is a storage device that can access the disks in the library
1
at high speed. Reference numeral
24
designates a network that is connected to the server
19
, and numerals
25
to
28
designate terminal units that read out the files in the server
19
through the network
24
. In this case, the data recorded on the disks are moving picture files which are rapidly increasing in recent years, and in order to perform continuous playback, the data should be transferred at a constant transfer rate or more.
A description is given of the operation when the server for library
19
with the construction described above plays back a file that is recorded on a disk in the library
1
, according to a request from a terminal unit.
One of the terminal units
25
to
28
specifies a file name of a file to be played back and makes a playback request of the file to the server
19
Through the network
24
. Referring to the contents of the disks in the library
1
that are recorded on the hard disk
20
, the server
19
reads out information of the files recorded on the disks
2
to
6
, and examines which of tho disks has the desired file. Then, when finding information of the desired file, the server
19
transfers control data to the arm control unit
17
of the library
1
through the bus
18
. In the library
1
, the arm control unit
17
moves the arm
16
according to the control data. The arm
16
removes tile disk including the desired file from the disk storage unit
11
to convey and insert the disk into one of the drives
12
to
15
.
When readout of the desired file in the disk starts, tell server
19
adds a network address to the data to output the data with the network address to the network
24
. The terminal unit. that has requested the file with the same network address receives this data to perform playback of the data.
In such a construction, when files in disks are read out and transferred to terminal units, disks in a library that can be removed from drives are generally lower in access speed than a hard disk or the like. In addition, in order to continuously playback specified moving picture data, it is required to transfer the data at a constant transfer rate or more. Therefore, in a case of media in which the access speed is low, such as the disks in the library, when a plurality of files in one disk are simultaneously read out, the transfer rate is not satisfactory for playback of moving picture data because of the slow readout. As a result, in playing back the moving picture data in terminal units, there occur the defects that, for example, the moving pictures impermanently stop. Consequently, it is usual to set the number of simultaneous readout files in one disk, which number is capable of transferring the moving pictures without producing the defects in the terminal units. Generally, the number of simultaneous readout files is set to 1. That is, concerning the disks in the library, a plurality of files in one disk cannot be simultaneously read out.
Meanwhile, concerning data that are recorded in a storage device in which the readout speed is high, such as a hard disk, it is possible to read out and transfer a plurality of files in the identical modium according to a plurality of playback requests, and perform continuous regeneration.
In a conventional server device, in order to accept requests from a plurality of terminal units as many as possible, a part of files that are retained in a library is copied to a hard disk. More specifically, the server device keeps records of the files that have received playback requests from the terminal units, in the hard disk, and frequency information about playback request frequency of the files in the library is created at regular intervals on the basis of the records of the playback requests. The files of high frequency in playback request are copied from the disks including tho files to the hard disk. Thereby, the plurality of files are read out of the hard disk in which the access speed is high to output moving pictures to the terminal units.
Further, for example, as disclosed by Japanese Published Patent Application No. Hei. 8-54991, one of disk media that has been read/written is left as it is inserted into a drive, and when data in the disk medium receive an access request, the data can be read/written immediately, thereby improving the access performance.
In the conventional server for library constructed as described above, the files of high frequency in playback request from the terminal units are successively copied from the disks to the hard disk. However, since the capacity of the hard disk is smaller than the capacity of the library, the hard disk is full of the files in a short time, failing to copy the files any more. In order to avoid this problem, among the files that have been copied to the hard disk, the files of low frequency in playback request are erased. As a result, however, only very few files of the files that have been retained in the library can be copied and retained in the hard disk, so that acceptance of the requests from the plurality of terminal units is restricted depending on the capacity of the hard disk.
Even when the operator of the server for library predicts that a file that is newly recorded in the library will receive many playback requests, or that a file will receive few playback requests in the future, there is no means of reflecting the prediction, and the operator only waits an increase or reduction in the playback
Yamada Takahiro
Yamaguchi Masashi
Channavajjala Srirama
Choules Jack
Matsushita Electric - Industrial Co., Ltd.
Parkhurst & Wendel L.L.P.
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