JP5413599B2 - Data distribution system, load balancing method and storage server - Google Patents

Description

  The present invention relates to a data distribution system, a load distribution method, and a storage server that store and distribute data in a plurality of servers in response to access from a client terminal via a network.

  A system in which data requested by a client terminal via a network is stored in a server, and data requested by a client terminal via a network is distributed from the server to the client terminal has been put into practical use in various fields. . For example, as a system for storing and distributing video data, a video on demand system, a video server system for a broadcasting station, a monitoring system for disaster prevention and crime prevention, and the like can be given.

  In this specification, these systems are referred to as “data distribution systems (especially, video data distribution systems for storing and distributing video data)”. Further, in this specification, a server that stores and distributes data in these systems is referred to as a “storage server”.

  In such a data distribution system, in order to process access from a client terminal at high speed, it is often the case that a plurality of storage servers are provided and data is distributed and stored in these storage servers.

  However, when frequently accessed data (for example, video data with high news properties) is stored in a specific storage server among a plurality of storage servers, access is biased to the storage server, The load on the storage server increases. For this reason, sufficient access performance cannot be exhibited as a whole system.

  Therefore, a technique for distributing the load to each storage server in such a data distribution system has been conventionally proposed. For example, in Patent Document 1, a dedicated management server is provided separately from a plurality of storage servers, and information related to each storage server is installed in the management server as a database, and the load status of each storage server is managed. Is described.

JP-A-10-320261

  However, in the technique described in Patent Document 1, since the management server manages a large number of storage servers, if access from client terminals concentrates on the management server, the load on the management server increases. As a result, since the management server cannot quickly manage the load status of each storage server, the access to the storage server storing video data with high access frequency is biased and the load on the storage server increases. End up.

  In view of the above points, the present invention provides a storage server and a load on each storage server in a data distribution system that stores and distributes data using a plurality of storage servers in response to access from a client terminal via a network. It aims at distributing the load of the server which has the function which manages a condition.

Storage server Ru engaged to the present invention transmits information of the load status of the self storage server to all other storage server stores information load status received from another storage server to all servers load management unit. And accumulation server, when receiving an access from the client terminal based on the information of the load status stored in all servers load management unit, the lowest storage server loads among self all storage server storage server is If a response is sent back to the client terminal and a read request is received from the client terminal, the storage server of its own stores the video to be read based on the load status information stored in all server load management units. When the storage server has the lowest load among all the storage servers storing data, a response is returned to the client terminal. Also, the master / copy server management unit manages the setting information of which storage server is the copy source of video data and which storage server is the copy destination of video data among a plurality of storage servers. To do. When the storage server uses data as a unit of access from the client terminal as content, the content load management unit manages the load status for each content in its own storage server. In addition, after the storage server returns the response to the write request from the client terminal, the data is written, and then the own storage server makes a copy based on the setting information managed by the master / copy server management unit When the data is set as the original, the written data is transferred to the storage server set as the copy destination, and the content load management unit determines that there is data whose load exceeds the predetermined threshold In addition, based on the load status information stored in the all server load management unit, the threshold value is exceeded for the storage server with the lowest load among all other storage servers that do not store data exceeding the threshold value. The data being transferred.

  According to the present invention, in a data distribution system in which data is stored and distributed by a plurality of storage servers in response to access from a client terminal via a network, the load status of the storage server and each storage server is managed. It is possible to distribute the load of servers having functions.

It is a figure which shows the whole structure of the video data delivery system which concerns on one embodiment of this invention. It is a figure which shows the structure of a management storage server. It is a figure which shows the image of the information sharing process between management storage servers. It is a figure which shows the image of the process at the time of the write request from a client terminal. It is a figure which shows the image of the process at the time of the read request from a client terminal. It is a flowchart which shows the process at the time of access of a client terminal. It is a flowchart which shows the process of the management storage server at the time of the access from a client terminal. It is a flowchart which shows the process of the management storage server of the information transmission side in an information sharing process. It is a flowchart which shows the process of the management storage server by the side of information in an information sharing process. It is a figure which shows the image of the copy video data transfer process at the time of high load to video data. It is a flowchart which shows the process of the management storage server of the transmission side at the time of request | requiring video data copy transfer. It is a flowchart which shows the process of the management storage server of the receiving side at the time of requesting video data copy transfer.

  Hereinafter, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described with reference to FIGS.

<System configuration>
FIG. 1 shows an example of the overall configuration of a video data distribution system 100 according to an embodiment of the present invention.
The video data distribution system 100 includes a management storage server 101, a storage 102, a plurality of management storage servers 103, and a plurality of storages 104. The video data distribution system 100 stores and distributes video data by a plurality of management storage servers 101 and 103 connected to the network in response to an access from a client terminal via the network.

  Each management storage server 101, 103 is connected to a network (a wide area network or a network using a dedicated line). A plurality of client terminals 105 are also connected to this network. As will be described in detail later, each management storage server 101, 103 manages the load status of all the management storage servers 101, 103 constituting the video data distribution system 100 to the storage server that stores and distributes data. The management server functions are combined.

  Each of the storages 102 and 104 uses a large-capacity video recording device such as a hard disk device having a RAID configuration. The storage 102 is connected to the management accumulation server 101. Each storage 104 is connected to one management storage server 103.

  In FIG. 1, the management storage server 101 and the storage 102 are expressed as “master” and one management storage server 103 and the storage 104 are expressed as “copy”. The meaning of the master and copy will be described later. .

FIG. 2 shows an internal configuration example of the management storage server 101.
However, since the management storage servers 101 and 103 have the same configuration, only the management storage server 101 will be described here.

  The management storage server 101 is provided with a management unit 202 composed of a microprocessor and a storage unit 213 composed of a recording device such as a hard disk device.

  The management unit 202 is a processing unit that performs predetermined processing, such as a video data location management unit 203, a video data access management unit 204, an all management storage server load management unit 205, a master / copy server management unit 206, and a transfer A control unit 211 and a content load management unit 212 are provided. In addition, the management unit 202 includes a video data location information database 207, a total management storage server load information database 208, a video data access information database 209, and a master / copy server information database 210 as databases for storing data. Prepare. The processing of each unit and information stored in each database are realized by the management unit 202 loading a program or database stored in the storage unit 213.

  The video data location management unit 203 stores video data of what file name and how much capacity in each directory of a storage (storage 102 in the management storage server 101) connected to its own management storage server. It is a program to manage what is. The video data location information database 207 is a database used by the video data location management unit 203 to perform this management.

  The video data access management unit 204 accepts access from the client terminal 105, and based on the load status information stored in the all management storage server load management unit 205, the video data access management unit 204 is one of all the storage servers 101. This is a program for returning a response to the client terminal when the storage server 101 has the lowest load. The video data access management unit 204 is a program for managing the number of accesses from the client terminal 105 to its own management storage server. The video data access information database 209 is a database used by the video data access management unit 204 to manage the number of accesses.

  The all management storage server load management unit 205 is a program for managing the load status of all the management storage servers 101 and 103 constituting the video data distribution system 100. The all management storage server load management unit 205 transmits the load status information of its own storage server 101 to all the other storage servers 101 and stores the load status information received from the other storage servers 101. The all management storage server load information database 208 is a database used by the all management storage server load management unit 205 to perform this management.

  The master / copy server management unit 206 is a program that manages setting information indicating which storage server is a copy source of video data and which storage server is a copy destination of video data. In addition, the master / copy server management unit 206 includes which management storage server of the video data distribution system 100 is a video data copy source (master) and which management storage server is a video. This is a program for managing setting information as to whether data is a copy destination (copy). The master / copy server information database 210 is a database used by the master / copy server management unit 206 to perform this management.

  Note that which management storage server is set as a master and which management storage server is set as a copy is determined by a setting operation of a system administrator. In FIG. 1, among the plurality of management storage servers 101 and 103 constituting the video data distribution system 100, the management storage server 101 set as a master by this setting operation (and the storage connected to the management storage server 101) 102) is expressed as a master. A plurality of management storage servers 103 (and storages 104 connected to the management storage server 103) set as copies by the setting operation of the system administrator are referred to as copies.

  When the own management storage server (in this example, the management storage server 101) is set as the master, the transfer control unit 211 sets the video data written in the own management storage server as a copy. This is a program for transferring to the management storage server (in this example, the management storage server 103). The transfer control unit 211 is managed by the master / copy server management unit 206 after data is written by the video data access management unit 204 returning a response to the write request from the client terminal 105. Based on the setting information, when the own storage server 101 is set as the copy source, the written data is transferred to the storage server 101 set as the copy destination.

  The content load management unit 212 is a program for managing the load status for each content (video data that is a unit of access from the client terminal 105) in its own management storage server.

<Information sharing process and access process>
Next, information sharing processing and processing at the time of access from a client terminal in the video data distribution system 100 will be described.

FIG. 3 shows an image of information sharing processing between the management storage servers 101 and 103.
In the management storage server 101, the all management storage server load management unit 205 shown in FIG. 2 transmits the load status notification 301 of its own management storage server to all other management storage servers 103 by multicast. Although not shown, in each management storage server 103, in the same manner, all management storage server load management units 205 notify the load status of their management storage servers to all other management storage servers. Is sent by multicast. Then, in each of the management storage servers 101 and 103, the all management storage server load management unit 205 receives the load status notification from each of the other management storage servers and receives information on the load status of all the management storage servers 101 and 103. Share

  In FIG. 3, the management storage servers 101 and 103 and the storages 102 and 104 constituting the video data distribution system 100 as a whole are viewed as one virtual management storage when viewed from the client terminal 105 side. It is shown as an all management storage server 304 that is a server. The same applies to FIGS. 4, 5 and 10 below.

FIG. 4 shows an image of processing at the time of a write request from the client terminal 105.
The client terminal 105 transmits a write destination request 401 to all management storage servers 304 by multicast.

  In each of the management storage servers 101 and 103, the video data access management unit 204 (FIG. 2) receives this write destination request 401, and manages all of the management storage server load management units 205 (FIG. 2). The storage server inquires whether the load is the lowest among all the management storage servers 101 and 103. The all management storage server load management unit 205 holds the load status information of all the management storage servers 101 and 103 by the information sharing process shown in FIG. 3, and responds to the inquiry based on the information.

  Then, as a result of this reply, the video data access management unit 204 of the management storage server (load management storage server 101 as an example in FIG. 4) with the lowest load is sent to the client terminal 105 that is the source of the write destination request 401 In response, a write destination response 402 is returned. Thereafter, the client terminal 105 writes 403 video data to the storage 102 connected to the management storage server 101 that has returned the write destination response 402.

  In the management storage server 101, the master / copy server management unit 206 (FIG. 2) manages that its own management storage server is set as a master and the management storage server (copy) 103 is set as a copy. . Therefore, in the management storage server 101, the video data access management unit 204 requests the transfer control unit 211 (FIG. 2) to transfer the video data written in the storage 102 to the management storage server (copy) 103. To do. In response to this request, the transfer control unit 211 creates a copy material by transferring 404 video data to the storage (copy) 104 connected to the management storage server (copy) 103.

FIG. 5 shows an image of processing at the time of a read request from the client terminal 105.
The client terminal 105 transmits a read destination request 501 to all the management storage servers 304 by multicast.

  In each of the management storage servers 101 and 103, the video data access management unit 204 receives the read destination request 501, and sends it to the video data location management unit 203 and all the management storage server load management units 205. Makes an inquiry as to whether it is the management storage server having the lowest load among all the management storage servers storing the video data to be read. The all management storage server load management unit 205 replies to the inquiry based on the information held by the information sharing process of FIG.

  Then, as a result of this reply, the video data access management unit 204 of the management storage server (in FIG. 5, the management storage server (copy) 103 as an example) having the lowest load is the client of the transmission source of the read destination request 501 A read destination response 502 is returned to the terminal 105.

  The client terminal 105 reads the video data 503 from the storage (copy) 104 connected to the management storage server (copy) 103 that returned the read destination response 502.

  3 to 5 show the image of the processing. Next, these processing will be described with reference to flowcharts. FIGS. 6 and 7 are flowcharts showing processing at the time of access (write request or read request) from the client terminal in FIGS. 4 and 5 as processing on the client terminal side and processing on the management storage server side.

FIG. 6 shows an example of video data access processing of the client terminal 105.
When accessing the video data, the client terminal 105 transmits a write destination request and a read destination request to all the management storage servers 304 by multicast (step S1).

  Then, the client terminal 105 receives a write destination response or a read destination response from the management storage server having the lowest load among the management storage servers 101 and 103 (step S2). Then, the client terminal 105 writes or reads video data to or from the management storage server (step S3), and ends the process.

FIG. 7 shows an example of video data access processing of the management storage server.
First, in each of the management storage servers 101 and 103, the video data access management unit 204 (FIG. 2) receives a write destination request or a read destination request from the client terminal 105 by multicast (step S11).

  Next, the video data access management unit 204 has the same load among all management storage servers 101 and 103 as to which one of the management storage servers 101 and 103 has a load on the management management server load management unit 205 (FIG. 2). An inquiry is made as to whether the load is the lowest (however, in the case of a read destination request, the load is the lowest among all the management storage servers storing the video data to be read). Then, the all management storage server load management unit 205 replies to the inquiry (step S12).

  As a result of this reply, if the load on the own server is not the lowest, the processing is terminated as it is. On the other hand, if the load is the lowest, the video data access management unit 204 returns a write destination response or a read destination response to the client terminal 105 (step S13).

  Subsequently, the video data access management unit 204 determines whether the access from the client terminal 105 is a write destination request (step S14). If the access is a write destination request, the video data access management unit 204 determines whether its own management storage server is set as the master (set as the master) with respect to the master / copy server management unit 206 (FIG. 2). If it is, which management storage server is set as a copy) is inquired. Then, the master / copy server management unit 206 replies to the inquiry (step S15).

  As a result of this response, if the master is set, the video data access management unit 204 accepts the writing of the video data from the client terminal 105, and the management storage server set as a copy for the transfer control unit 211 Request transfer of video data to In response to this request, the transfer control unit 211 creates a copy material by transferring the video data written in the storage 102 to the storage 104 connected to the management storage server 103 set as a copy ( Step S16). Then, the process ends.

  As a result of the response in step S15, if not set to the master, the video data access management unit 204 accepts writing of video data from the client terminal 105 (step S17), and ends the process.

  If the access is a read destination request in step S14, the video data access management unit 204 accepts the video data read by the client terminal 105 (step S18) and ends the process.

  FIGS. 8 and 9 are flowcharts showing the processing of the management storage server on the information transmission side and the processing of the management storage server on the information reception side in the information sharing processing of FIG.

FIG. 8 shows an example of processing on the transmission side of the information sharing of the management storage server.
In each of the management storage servers 101 and 103, the total management storage server load management unit 205 makes the current number of accesses (the number of writes and the number of reads) from the client terminal 105 to its own management storage server to the video data access management unit 204. )

  Also, the total management storage server load management unit 205 gives the video data location management unit 203 the current disk usage (how much video data of what file name is stored in the storage connected to the management storage server of its own). Inquire about whether the capacity of The video data access management unit 204 and the video data location management unit 203 calculate the current number of accesses and disk usage, respectively, and reply to the total management storage server load management unit 205 (step S21).

  Based on this response, the total management storage server load management unit 205 stores the current number of accesses and disk usage in the total management storage server load information database 208 as information on the load status of its own management storage server. A load status notification of its own management storage server that contains the number of accesses and the amount of disk usage is transmitted to all the management storage servers other than itself by multicast (step S22).

  The all management storage server load management unit 205 waits for a certain time (for example, 5 to 10 seconds) (step S23), and then returns to step S21 again to periodically repeat the processes of steps S21 to S22. Note that, for example, UDP (User Datagram Protocol) is used as a communication protocol for making this inquiry. For this reason, compared with the case where TCP (Transmission Control Protocol) is used, communication load can be restrained low.

FIG. 9 shows an example of processing on the receiving side of information sharing of the management storage server.
In each of the management storage servers 101 and 103, the all management storage server load management unit 205 receives a load status notification from another management storage server (step S31).

  At this time, each management storage server 101, 103 stores the number of accesses and the disk usage indicated by the load status notification in the all management storage server load information database 208 as information on the current load status of the management storage server. (Step S32), and the process ends.

  As described with reference to FIGS. 3 to 9, in the video data distribution system 100, each management storage server 101, 103 has a function as a storage server that stores and distributes data. Further, the video data distribution system 100 also has a function as a management server that manages the load status of all the management storage servers 101 and 103 by the all management storage server load management unit 205.

  At the time of a video data write request from the client terminal 105, the client terminal 105 transmits a write destination request to all the management storage servers 101 and 103 by multicast, and only the management storage server with the lowest load is the client. A write destination response is returned to the terminal 105.

  As a result, when a video data write request from the client terminal 105 is requested, the load on a specific management storage server is prevented from increasing, and the load is distributed to each management storage server. Therefore, the load of the server having the function as the storage server is distributed, and unlike the case where the dedicated management server is provided, the load of the server having the function of managing the load status of all the storage servers is also distributed.

  When the video data is written, if the management storage server that has returned the write destination response to the client terminal 105 is set as a master, the written video data is transferred to the management storage server set as a copy. Thus, a copy material is created.

  When the client terminal 105 requests video data to be read, the client terminal 105 transmits a read destination request to all the management storage servers 101 and 103 by multicast. Of all the management storage servers that store the video data to be read (the management storage server in which the video data is written from the client terminal 105 and the management storage server in which the copy material of the video data is created) Only the management storage server with the lowest load returns a read destination response to the client terminal 105.

  As a result, even when the video data is requested to be read from the client terminal 105, the load on a specific management storage server is prevented from increasing, and the load is distributed to a plurality of management storage servers.

  In this way, in this video data distribution system 100, the load of the management storage server is distributed both when the video data is requested to be written and when it is read from the client terminal 105. Therefore, the access performance of the entire system is improved. Can be improved.

  Furthermore, conventionally, when an additional storage server is added, information about the additional storage server must be newly installed as a database on the management server. During this time, the operation of the management server is stopped to stop system operation. I had to.

  In contrast, in this video data distribution system 100, each management storage server transmits a load status notification of its own management storage server by multicast at regular intervals. Therefore, even if the management storage server is expanded while the system is operating, the existing management storage server receives the load status notification transmitted by multicast from the expanded management storage server, thereby increasing the management storage server Can manage the load situation. Further, the added management storage server can also manage the load status of the existing management storage server by receiving the load status notification transmitted by multicast from the existing management storage server.

  Thereby, in this video data distribution system 100, when adding the management storage server, the management storage server is added without stopping the operation of the system, and each management storage server (existing management storage server and the added management storage server) is added. Management storage server) can manage the load status of all management storage servers.

  In view of the above, this video data distribution system 100 is a system that varies in the number of distribution requests for stored video data, such as a video-on-demand system, a video server system for broadcasting stations, or for disaster prevention / crime prevention. It can be applied to systems that are required to operate without interruption from the standpoint of broadcasting schedules or disaster prevention / crime prevention, such as surveillance systems.

<Copy video data transfer processing under high load on video data>
Next, a copy video data transfer process when the video data distribution system 100 is heavily loaded with video data will be described.

  FIG. 10 shows an image of the copy video data transfer process when the video data is heavily loaded.

  For example, in the management storage server 101, when the content load management unit 212 determines that the number of accesses to specific video data in the video data in the storage 102 is large, in the management storage server 101, the transfer control unit 211 Then, a video data copy transfer request 601 with the video data as the master video data 110 is transmitted to the management storage server 103 having the lowest load among the management storage servers 103 that have not yet stored the master video data 110. Then, the management storage server 103 returns a video data copy transfer response 602 to the management storage server 101.

  When the management storage server 101 receives the video data copy transfer response 602, the transfer control unit 211 transfers the video data copy transfer to the storage 104 connected to the management storage server 103 that is the return source of the video data copy transfer response 602. By performing 603, copy video data 111 is created.

  FIGS. 11 and 12 are flowcharts showing the processing of the management storage server on the request transmission side and the processing of the management storage server on the request reception side in the copy video data transfer processing of FIG.

FIG. 11 shows a processing example of the management storage server on the transmission side when requesting video data copy transfer.
In each of the management storage servers 101 and 103, the content load management unit 212 monitors the load (number of accesses) for each content of video data in the storage connected to its own management storage server at regular intervals (step S41). ), It is determined whether or not there is content that exceeds a predetermined threshold in the number of accesses for each content (step S42).

  If there is no content exceeding the threshold, the process is terminated as it is. On the other hand, if there is content that exceeds the threshold value, the content load management unit 212 instructs the all management storage server load management unit 205 to load the load among all other management storage servers that have not stored the content. Queries which management storage server is the lowest management storage server (excluding the management storage server that failed to copy transfer once in the same process). Then, when the all management storage server load management unit 205 replies to the inquiry, the content load management unit 212 acquires information indicating the management storage server to be the copy transfer destination (step S43).

  Subsequently, the content load management unit 212 instructs the transfer control unit 211 to copy and transfer the content to the management storage server indicated by the acquired information (step S44).

  The transfer control unit 211 transmits a copy transfer request to the video data access management unit 204 of the management storage server that is the destination of copy transfer in accordance with the instruction from the content load management unit 212 (step S45). Then, the transfer control unit 211 determines whether a response indicating normality is returned from the video data access management unit 204 that is the transmission destination of the copy transfer request (step S46).

  If a response indicating normality is returned, the transfer control unit 211 sends a response to the storage 104 connected to the management storage server that is the destination of copy transfer in the instruction from the content load management unit 212. Then, copy transfer of the content is performed (step S47). Then, the transfer control unit 211 notifies the content load management unit 212 of the copy transfer result (here, the copy transfer was successful) (step S48).

  On the other hand, if a response indicating normality is not returned in step S46, the transfer control unit 211 proceeds from step S46 to step S48 as it is, and the copy transfer result (here, copy transfer has failed). Is sent to the content load management unit 212.

  The content load management unit 212 determines whether or not the copy transfer result indicates that the copy transfer was successful (step S49). If the copy transfer is successful, the content load management unit 212 ends the copy transfer process (step S50). On the other hand, if the copy transfer fails, the content load management unit 212 returns to step S44 again and repeats the processing from step S44.

FIG. 12 shows a processing example of the management storage server on the receiving side when requesting video data copy transfer.
In each of the management storage servers 101 and 103, when the video data access management unit 204 receives a copy transfer request from the transfer control unit 211 of another management storage server (step S61), it configures its own management storage server. It is determined whether the hardware status information is normal (step S62).

  If it is normal, the video data access management unit 204 sends the content information (content name and directory name for storing the content) requested to be transferred to the video data location management unit 203 to the video data location information database 207. Is written (step S63). Then, the video data access management unit 204 returns a response result indicating normality to the transfer control unit 211 of the management storage server that is the transmission source of the copy transfer request (step S64).

  Subsequently, the transfer control unit 211 accepts copy transfer from the management storage server that is the source of the copy transfer request (step S66). When the copy transfer is completed, the transfer control unit 211 detects the completion of the copy transfer (step S67) and ends the process.

  In step S62, if the hardware status information is not normal, the video data access management unit 204 returns a response result indicating abnormality to the transfer control unit 211 of the management storage server that is the source of the copy transfer request. (Step S65). Then, the process ends.

  As described above with reference to FIGS. 10 to 12, in the video data distribution system 100, even for the management storage server that is not set as the master among the management storage servers 101 and 103, the load on certain specific video data When (the number of accesses) becomes high, a copy material is created by transferring the video data to the management storage server with the smallest load among the management storage servers not storing the video data.

  As a result, even if the number of accesses to the specific video data continues to be large thereafter, the load on the management storage server is distributed, so that the access performance of the entire system can be improved.

<Modification>
In the above embodiment, the present invention is applied to the video data distribution system 100. However, the present invention is not limited to the video data distribution system 100, and may be applied to a data distribution system that stores and distributes data other than video data (for example, audio data other than video content, content, programs, and the like). .

  Further, the present invention is not limited to the above-described embodiments, and it is needless to say that other various application examples and modifications can be taken without departing from the gist of the present invention described in the claims.

  DESCRIPTION OF SYMBOLS 100 ... Video data delivery system, 101 ... Management storage server, 102 ... Storage, 103 ... Management storage server, 104 ... Storage, 105 ... Client terminal, 202 ... Management part, 203 ... Video data location management part, 204 ... Video data access Management unit, 205 ... All management storage server load management unit, 206 ... Master / copy server management unit, 207 ... Video data location information database, 208 ... All management storage server load information database, 209 ... Video data access information database, 210 ... Master / copy server information database, 211 ... transfer control unit, 212 ... content load management unit, 213 ... storage unit, 304 ... all management storage server

Claims (3)

In a data distribution system for storing and distributing data by a plurality of storage servers connected to the network in response to access from a client terminal via the network,
The storage server
All server load managers that transmit load status information of their own storage servers to all other storage servers and store load status information received from other storage servers;
When access from the client terminal is accepted, and based on the load status information stored in the all server load management unit, when the own storage server is the storage server with the lowest load among all the storage servers When a response is sent back to the client terminal and a read request is received from the client terminal, the storage server of its own stores the video data to be read based on the load status information stored in the all server load management unit. If it is the lowest storage server load among all the storage servers that have accumulated, and a data access management unit which returns a response to said client terminal,
A master / copy server management unit for managing setting information indicating which storage server is a copy source of video data and which storage server is a copy destination of video data among the plurality of storage servers;
A content load management unit for managing the load status of each content in its own storage server when data serving as a unit of access from the client terminal is content;
After the data access management unit returns a response to the write request from the client terminal, the data is written, and then based on the setting information managed by the master / copy server management unit, its own storage server Is written as the copy source, the written data is transferred to the storage server set as the copy destination, and there is data whose load exceeds a predetermined threshold by the content load management unit. If determined, based on the load status information stored in the all-server load management unit, the accumulation of the lowest load among all other accumulation servers not accumulating data exceeding the threshold A data distribution system comprising: a transfer control unit configured to transfer data exceeding the threshold value to a server . In a load distribution method in a data distribution system in which data is stored and distributed by a plurality of storage servers connected to the network in response to access from a client terminal via the network,
All server loads in which the storage server transmits the load status information of its own storage server to all other storage servers, and stores the load status information received from the other storage servers in all server load management units Administrative steps;
The storage server receives the access from the client terminal, and based on the load status information stored in the all server load management unit, the storage server having the lowest load among all the storage servers In the case where the response is returned to the client terminal and a read request is received from the client terminal, the own storage server reads the response based on the load status information stored in the all server load management unit. A data access management step of returning a response to the client terminal when the storage server has the lowest load among all the storage servers storing target video data ;
The storage server manages setting information as to which storage server is the video data copy source and which storage server is the video data copy destination among the plurality of storage servers by the master / copy server management unit. Master / copy server management step to perform,
A content load management step of managing a load status of each content in its own storage server by a content load management unit when the storage server uses data as a unit of access from the client terminal as content;
After data is written by the storage server returning a response to the write request from the client terminal, its own storage server is configured based on the setting information managed by the master / copy server management unit. When the copy source is set, the written data is transferred to the storage server set as the copy destination, and the content load management unit determines that there is data whose load exceeds a predetermined threshold. Storage server having the lowest load among all other storage servers that have not stored the data exceeding the threshold based on the load status information stored in the all server load management unit. And a transfer control step of transferring data exceeding the threshold . In a storage server that stores and distributes data in response to access from a client terminal via a network,
All server loads that transmit the load status information of their own storage server to all other storage servers connected to the network and store the load status information received from other storage servers connected to the network The management department,
Accepts access from the client terminal, and based on the load status information stored in the all server load management unit, its own storage server has the lowest load among all the storage servers connected to the network When the server is a storage server, a response is returned to the client terminal, and when a read request is received from the client terminal, the storage server of its own is based on the load status information stored in the all server load management unit. A data access management unit that returns a response to the client terminal when the storage server has the lowest load among all the storage servers storing video data to be read ;
A master / copy server management unit for managing setting information indicating which storage server is a copy source of video data and which storage server is a copy destination of video data among the plurality of storage servers;
A content load management unit for managing the load status of each content in its own storage server when data serving as a unit of access from the client terminal is content;
After the data access management unit returns a response to the write request from the client terminal, the data is written, and then based on the setting information managed by the master / copy server management unit, its own storage server Is written as the copy source, the written data is transferred to the storage server set as the copy destination, and there is data whose load exceeds a predetermined threshold by the content load management unit. If determined, based on the load status information stored in the all-server load management unit, the accumulation of the lowest load among all other accumulation servers not accumulating data exceeding the threshold A storage server comprising: a transfer control unit that transfers data exceeding the threshold to the server.

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