JP2011170667A - File-synchronizing system, file synchronization method, and file synchronization program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the efficiency of file synchronization. <P>SOLUTION: A transfer device 10 includes an actual data splitting unit 11 for splitting data in a file 141 to be transferred into a plurality of blocks; a hash-value creation unit 12 for creating a hash value out of the data for each block; and a transmission unit 13 for transmitting the hash value to the transfer device 20. The transfer device 20 includes an actual data splitting unit 21 for splitting the data in the file 241 into a block of the same size as the blocks split by the actual data splitting unit 11; a hash value creation unit 22 for creating a hash value out of the data for each block; and a transmission unit 23 for comparing for each block number the hash values generated by the hash value creation units 12, 22, and transmitting the block numbers of the unmatched hash values to the transfer device 10. The transmission unit 13 transmits the actual data corresponding to the block number received from the transfer device 20 to the transfer device 20. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a file synchronization system, a file synchronization method, and a file synchronization program.

  When the same file is handled by a plurality of systems, file synchronization may be performed so that the contents of each file are the same. As a method of performing file synchronization, for example, there are a method of transferring and synchronizing the entire target file, and a method of transferring and synchronizing only difference information before and after updating of the target file. By adopting a method of transferring only the difference information, it becomes possible to shorten the turnaround time of the synchronization process.

  Patent Document 1 below discloses a system that performs file synchronization by transferring only difference information. In this system, the file transfer source device manages the files before and after the update, and transmits the difference data extracted from the files before and after the update to the transfer destination device. Then, the transfer destination apparatus performs file synchronization by generating the updated file using the difference data and the file before update.

JP 2003-337723 A

  In the system described in Patent Document 1, in addition to the updated file, the file before the update is managed. Therefore, an increase in storage area and an increase in file maintenance work, etc., are a factor that increases costs.

  SUMMARY An advantage of some aspects of the invention is that it provides a file synchronization system, a file synchronization method, and a file synchronization program capable of improving the efficiency of file synchronization.

  The file synchronization system of the present invention is a file synchronization system comprising a transfer source device and a transfer destination device each having a file to be synchronized with the file, wherein the transfer source device is a transfer source that is to be synchronized with the file. A first dividing unit that divides the data of the file into a plurality of blocks; a first generating unit that generates a hash value from data included in each block divided by the first dividing unit; A first transmission unit that transmits the hash value generated by one generation unit to the transfer destination device, and the transfer destination device stores the data of the file at the transfer destination that is the target of file synchronization, A second dividing unit that divides the blocks divided by the first dividing unit into blocks of the same size, and a block that is divided by the second dividing unit. A second generation unit that generates a hash value from each piece of data, a hash value generated by the first generation unit, and a hash value generated by the second generation unit, A second transmission unit that compares each block number that identifies a block including the original data and transmits the block number corresponding to the hash value that does not match to the transfer source device, and the transfer source The first transmission unit of the apparatus includes: transmitting data included in the block corresponding to the block number received from the transfer destination apparatus to the transfer destination apparatus.

  The file synchronization method of the present invention is a file synchronization method executed by a file synchronization system including a transfer source device and a transfer destination device each having a file to be synchronized with the file synchronization method, wherein the transfer source device performs file synchronization. A first division step of dividing the data of the transfer source file as a target into a plurality of blocks, and a first value for generating a hash value from the data included in each block divided in the first division step Performing a generation step and a first transmission step of transmitting the hash value generated in the first generation step to the transfer destination device, wherein the transfer destination device is a destination of a file synchronization target Dividing the file data into blocks of the same size as the blocks divided in the first dividing step; A second generation step for generating a hash value from data included in each block divided in the second division step, the hash value generated in the first generation step, and the second The hash value generated in the generating step 2 is compared for each block number that identifies the block including the generation data of each hash value, and the block number corresponding to the hash value that does not match is compared with the transfer source. A second transmission step of transmitting to the device, wherein the first transmission step of the transfer source device transfers the data included in the block corresponding to the block number received from the transfer destination device. Send to the destination device.

  The file synchronization program of the present invention causes a computer to execute each step included in the file synchronization method.

  According to the present invention, the efficiency of file synchronization can be improved.

It is a block diagram which illustrates the composition of the file synchronization system in an embodiment. It is a figure which illustrates the data structure of the hash value production | generation rate table in a transfer origin apparatus. It is a figure which illustrates the data structure of the transfer rate table in a transfer source apparatus. It is a figure which illustrates the data structure of the hit rate table in a transfer origin apparatus. It is a figure which illustrates the data structure of the hash value generation rate table in a transfer destination apparatus. It is a flowchart for demonstrating the process sequence of the file transfer in a file synchronous system. It is a flowchart for demonstrating the process sequence of the difference transfer contained in the process sequence of FIG.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a file synchronization system, a file synchronization method, and a file synchronization program according to the present invention will be described with reference to the accompanying drawings.

  First, the configuration of the file synchronization system in the embodiment will be described. FIG. 1 is a block diagram illustrating a configuration of a file synchronization system in the embodiment. As shown in FIG. 1, the file synchronization system 1 includes a transfer source device 10 and a transfer destination device 20. The transfer source device 10 and the transfer destination device 20 are connected via a network 30.

  The transfer source device 10 and the transfer destination device 20 respectively include files 141 and 241 that are subject to file synchronization. In the present embodiment, for convenience of explanation, a case where the updated information is reflected in the file 241 of the transfer destination apparatus 20 when the file 141 of the transfer source apparatus 10 is updated will be described. When the file 241 of the transfer destination apparatus 20 is updated and the updated information is reflected in the file 141 of the transfer source apparatus 10, each function of the transfer source apparatus 10 described below and the transfer destination apparatus 20 This can be realized by replacing each function. The transfer source device 10 and the transfer destination device 20 can be provided with respective functions.

  Here, the transfer source device 10 and the transfer destination device 20 physically include, for example, a CPU (Central Processing Unit), a storage device, and an input / output interface. The storage device includes, for example, a ROM (Read Only Memory) and HDD (Hard Disk Drive) that store programs and data processed by the CPU, and a RAM (Random Access Memory) mainly used as various work areas for control processing. ) Etc. are included. The HDDs of the transfer source device 10 and the transfer destination device 20 store files 141 and 241 that are subject to file synchronization, respectively. Each function of the transfer source device 10 and the transfer destination device 20 described later is realized by the CPU executing the program stored in the ROM and processing the data expanded in the RAM. Note that the file synchronization target file is not limited to one set, and a plurality of sets can be set.

  The transfer source device 10 includes a real data dividing unit 11, a hash value generation unit 12, a transmission unit 13, a storage unit 14, and a transfer selection unit 15.

  The actual data dividing unit 11 divides the actual data of the transfer source file 141 to be subjected to file synchronization into a plurality of blocks. The number of blocks to be divided is preset as the number of divided blocks N and is stored in the storage unit 14. Each block divided into N blocks is assigned a block number for identifying the block. The actual data dividing unit 11 temporarily stores the size of each block in the storage unit 14 as a divided block size D.

  The hash value generation unit 12 generates a hash value from the actual data included in each block divided into N blocks by the actual data dividing unit 11. The hash value is generated by inputting each real data to a predetermined hash function. The hash value generation unit 12 calculates the hash value generation time by accumulating the time required for generating the hash value. The hash value generation unit 12 generates a new value in the hash value generation rate table on the transfer source side illustrated in FIG. 2 using the file size A and the hash value generation time after generating the hash value from the actual data of all blocks. to add.

  The hash value generation rate table on the transfer source side illustrated in FIG. 2 includes, for example, a transfer process name item, a file size item, a hash value generation time item, and a weighting item as data items. The transfer process name item stores information for identifying the transfer process. The file size item stores the file size of the transfer source file. The accumulated time item stores an accumulated value of time required when the hash value generating unit 12 generates the hash value. The weighting item stores the weight given to each record when the hash value generation rate is calculated using each record. The weighting is set so that the newly generated record becomes larger. This makes it possible to calculate a generation rate that reflects the latest transfer status.

  The transmission unit 13 transmits a hash value acquisition request to the transfer destination device 20. The hash value acquisition request includes, for example, the hash value generated by the hash value generation unit 12, the file name of the transfer source file 141, the file size A, the number of divided blocks N, the divided block size D, and the hash value size S. . The file name, file size A, and hash value size S are set in advance and stored in the storage unit 14.

  The transmission unit 13 transmits the actual data included in the block corresponding to the block number received from the transfer destination device 20 to the transfer destination device 20. The transmitter 13 calculates the transfer data size by adding up the sizes of the transmitted actual data, and calculates the transfer time by adding up the time required for transmitting the actual data. After transmitting all the actual data to be transferred, the transmitter 13 adds a new record to the transfer rate table shown in FIG. 3 using the calculated transfer data size and transfer time.

  The transfer rate table shown in FIG. 3 includes, for example, a transfer process name item, a transfer data size item, a transfer time item, and a weighting item as data items. The transfer process name item stores information for identifying the transfer process. The transfer data size item stores an integrated value of the size of actual data transmitted by the transmission unit 13. The transfer time item stores an integrated value of the time required when the transmission unit 13 transmits actual data. The weighting item stores the weight given to each record when the transfer rate is calculated using each record. The weighting is set so that the newly generated record becomes larger. This makes it possible to calculate a generation rate that reflects the latest transfer status.

  After transmitting all the actual data to be transmitted, the transmitting unit 13 adds a new record to the hit rate rate table shown in FIG. 4 using the file size A and the transfer data size.

  The hit rate table shown in FIG. 4 includes, for example, a transfer file name item, a file size item, and a hit size item as data items. The transfer file name item stores the name of the transfer source file. The file size item stores the file size of the transfer source file. The hit size item stores a value obtained by subtracting the transfer data size transmitted by the transmission unit 13 from the file size of the transfer source file, that is, the actual data size that has not been transmitted among the actual data of the transfer source file.

  The transfer selection unit 15 will be described later.

  The transfer destination device 20 includes an actual data dividing unit 21, a hash value generating unit 22, a transmitting unit 23, and a storage unit 24.

  The actual data dividing unit 21 divides the actual data of the transfer destination file 241 to be subjected to file synchronization into blocks having the same size as the blocks divided by the actual data dividing unit 11. The size of each block divided by the actual data dividing unit 11 is obtained by referring to the divided block size D received from the transfer source device 10.

  The hash value generation unit 22 generates a hash value from the actual data included in each block divided by the actual data dividing unit 21. The hash value is generated by inputting each real data to a predetermined hash function. The hash value generation unit 12 calculates the hash value generation time by accumulating the time required for generating the hash value. The hash value generation unit 22 adds a new record to the transfer destination side hash value generation rate table shown in FIG. 5 using the file size and the hash value generation time after generating hash values from the actual data of all blocks. To do.

  The hash value generation rate table on the transfer destination side illustrated in FIG. 5 includes, for example, a transfer process name item, a file size item, a hash value generation time item, and a weighting item as data items. The transfer process name item stores information for identifying the transfer process. The file size item stores the smaller file size of the file size of the transfer source file and the file size of the transfer destination file. The hash value generation time item stores an integrated value of time required when the hash value generation unit 22 generates a hash value. The weighting item stores the weight given to each record when the hash value generation rate is calculated using each record. The weighting is set so that the newly generated record becomes larger. This makes it possible to calculate a generation rate that reflects the latest transfer status.

  The transmission unit 23 compares the hash value generated by the hash value generation unit 12 and the hash value generated by the hash value generation unit 22 for each of the same block numbers, and the block corresponding to the hash value that does not match A response message including the number is transmitted to the transfer source device 10.

  The transfer selection unit 15 of the transfer source device 10 selects whether the transfer source file 141 is transmitted by normal transfer or differential transfer as a transfer method at the time of file synchronization. Normal transfer is a transfer process in which all actual data of a transfer source file is transmitted to a transfer destination device. Differential transfer is a transfer process in which actual data included in a data-updated block is transmitted to a transfer destination device.

  The transfer selection unit 15 selects differential transfer when the file size A of the transfer source file 141 is larger than the value obtained by multiplying the number of divided blocks N and the hash value size S. The transfer selection unit 15 selects normal transfer when the file size A of the transfer source file 141 is equal to or smaller than the value obtained by multiplying the number of divided blocks N and the hash value size S. When the total real data size is larger than the total hash value size, transfer efficiency can be improved by selecting differential transfer. On the other hand, when the total actual data size is equal to or smaller than the total hash value size, it is possible to prevent the transfer efficiency from being lowered due to the differential transfer by selecting the normal transfer.

  The transfer selection unit 15 estimates the estimated total processing time when the transfer source file 141 is normally transferred (hereinafter referred to as “normal transfer processing time”), and the estimated total processing time when the transfer source file 141 is differentially transferred. (Hereinafter referred to as “differential transfer processing time”), the differential transfer is selected. When the normal transfer processing time is equal to or shorter than the differential transfer processing time, the normal transfer is selected. Hereinafter, a method for calculating the normal transfer processing time and the differential transfer processing time will be described by taking as an example the case of transferring the transfer source file 141 from the transfer source device 10 to the transfer destination device 20.

  The normal transfer processing time can be calculated using the following equation 1, for example.

  Normal transfer processing time T1 = file size A / transfer rate R3 Equation 1

  The file size A in the above equation 1 is the file size of the transfer source file 141. The transfer rate R3 in Equation 1 can be calculated, for example, by substituting the data in the transfer rate table shown in FIG.

  Transfer rate R3 = Σ (transmission data size / transfer time × weighting) / Σ (weighting) Equation 2

  The difference transfer processing time can be calculated using, for example, the following Equation 3.

  Differential transfer processing time T2 = {Normal transfer processing time T1 × (1−Hit rate H)} + Hash value generation time T3 + Hash value transfer time T4 + Hash value generation time T5 + Message transmission time T6

  The hit rate H in Equation 3 above is the probability that the same data exists in the transfer source file 141 and the transfer destination file 241. For example, the hit rate table data shown in FIG. Can be calculated.

  Hit ratio H = file 141 hit size / file size A Equation 4

  The hash value generation time T3 in Expression 3 is a time required for generating the hash value in the transfer source device 10, and can be calculated using Expression 5 below, for example.

  Hash value generation time T3 = file size A / hash value generation rate R1 Equation 5

  The hash value generation rate R1 of the above formula 5 can be calculated by substituting the data of the hash value generation rate table shown in FIG.

  Hash value generation rate R1 = Σ (file size / hash value generation time × weighting) / Σ (weighting) Equation 6

  The hash value transfer time T4 in Equation 3 above is the time required to transfer the hash value from the transfer source device 10 to the transfer destination device 20, and can be calculated using the following Equation 7, for example.

  Hash value transfer time T4 = number of divided blocks N × hash value size S / transfer rate R3 Expression 7

  The hash value generation time T5 of the above formula 3 is a time required for generating the hash value in the transfer destination device 20, and can be calculated using the following formula 8, for example.

  Hash value generation time T5 = file size B / hash value generation rate R2 Equation 8

  The file size B in Expression 8 is the file size of the transfer destination file 241. The hash value generation rate R2 of Equation 8 can be calculated by substituting the data of the hash value generation rate table shown in FIG.

  Hash value generation rate R2 = Σ (file size / hash value generation time × weighting) / Σ (weighting) Equation 9

  The message transmission time T6 in the above equation 3 is the time required for transmitting various messages exchanged between the transfer source device 10 and the transfer destination device 20 during the transfer process, and is calculated using, for example, the following equation 10. can do.

  Message transmission time T6 = message data size C / transfer rate R3 Equation 10

  Examples of the various messages include a hash value acquisition request, a response message including a block number corresponding to a hash value that does not match.

  Next, the operation of the file synchronization system in the embodiment will be described. FIG. 6 is a flowchart for explaining a file transfer processing procedure in the file synchronization system.

  First, the transfer selection unit 15 of the transfer source device 10 acquires the file size A of the transfer source file 141 that is the target of file synchronization (step S101), and the file size A includes the number of divided blocks N and the hash value size S. It is determined whether or not the value is greater than the value obtained by multiplying (step S102). When this determination is NO (step S102; NO), the transfer selection unit 15 of the transfer source device 10 selects normal transfer and ends this processing procedure.

  On the other hand, when it is determined in step S102 that the file size A is larger than the value obtained by multiplying the divided block number N and the hash value size S (step S102; YES), the transfer selection unit 15 of the transfer source device 10 is determined. Transmits the file name of the transfer source file 141 to the transfer destination device 20 (step S103).

  Subsequently, based on the file name of the transfer source file 141, the transfer destination device 20 identifies the transfer destination file 241 set as a file synchronized with the transfer source file 141 (step S104), and the transfer destination file 241. File size B is transmitted to the transfer source device 10 (step S105).

  Subsequently, the transfer selection unit 15 of the transfer source device 10 determines whether or not the normal transfer processing time is longer than the differential transfer processing time (step S106). If this determination is NO (step S106; NO), the transfer selection unit 15 of the transfer source device 10 selects normal transfer and ends this processing procedure.

  On the other hand, if it is determined in step S106 that the normal transfer processing time is longer than the difference transfer processing time (step S106; YES), the transfer selection unit 15 of the transfer source device 10 selects the difference transfer and transfers the transfer. The source device 10 and the transfer destination device 20 execute differential transfer (step S107). The difference transfer processing procedure will be described below.

  FIG. 7 is a flowchart for explaining in detail the difference transfer processing procedure executed in step S107 of FIG.

  First, the actual data dividing unit 11 of the transfer source device 10 divides the actual data of the transfer source file 141 to be subjected to file synchronization into blocks corresponding to the number of divided blocks N (step S201).

  Subsequently, the hash value generation unit 12 of the transfer source device 10 generates the hash value by inputting the actual data included in each block divided into N pieces in step S201 to the hash function, and generates the hash value. Is accumulated (step S202).

  Subsequently, the transmission unit 13 of the transfer source device 10 transmits each hash value generated in step S202, the file name of the transfer source file 141, the file size A, the number of divided blocks N, the divided block size D, and the hash value size S. Is sent to the transfer destination device 20 (step S203).

  Subsequently, the actual data dividing unit 21 of the transfer destination device 20 divides the actual data of the transfer destination file 241 into blocks having the same size as the divided block size D based on the hash value acquisition request (step S204).

  Subsequently, the hash value generation unit 22 of the transfer destination device 20 generates the hash value by inputting the actual data included in each block divided in step S204 to the hash function, and is required for generation of the hash value. The time is integrated (step S205).

  Subsequently, the transmission unit 23 of the transfer destination apparatus 20 compares the hash value generated in step S202 and the hash value generated in step S205 for each same block number (step S206), and the comparison target The block number that does not match the hash value is identified (step S207). The transmission unit 23 transmits a response message including the block number identified as inconsistent to the transfer source device 10 (step S208).

  Subsequently, the transmission unit 13 of the transfer source device 10 transmits the actual data included in the block corresponding to the block number received from the transfer destination device 20 to the transfer destination device 20 (step S209), and sets the transfer time of the actual data. Integration is performed (step S210).

  As described above, according to the file synchronization system 1 in the embodiment, the transfer source device 10 can perform differential transfer by managing the updated file. Thereby, the storage area for managing the pre-update file and the difference information can be reduced, and the maintenance work for the pre-update file and the difference information can be omitted. Therefore, the efficiency of file synchronization can be improved.

  Such an effect is particularly effective when the file to be subjected to file synchronization is a file that stores a fixed-length record or a data write-once file. For example, when a specific record is updated in a file that stores a fixed-length record, only the actual data of the block including the updated record may be differentially transferred. When actual data is appended in a data appending type file, only the actual data of the block including the appended actual data need be differentially transferred. Thereby, the turnaround time of the synchronization process can be greatly shortened. Such an effect increases as the file capacity increases.

  Note that each of the above-described embodiments is merely an example, and does not exclude various modifications and technical applications that are not explicitly described in the embodiment. That is, the present invention can be implemented by being modified into various forms without departing from the spirit of the present invention.

  For example, in the above-described embodiment, when calculating the hash value generation rate and the transfer rate, weights are assigned to a plurality of past transfer processes. For example, only the latest transfer processes are weighted. Thus, no weighting may be given to other transfer processes. As a result, it is possible to calculate a rate that quickly reflects the usage status of the CPU and the usage status of the network. Further, for example, weighting may be equally applied to a plurality of past transfer processes. As a result, in an unstable environment where CPU usage and network usage change suddenly, the status of multiple past transfer processes is the same, regardless of only the latest transfer process status. It is possible to calculate a rate in consideration of

  A part or all of the above embodiments can be described as in the following supplementary notes, but the present invention is not limited to the following.

  (Supplementary note 1) A file synchronization system including a transfer source device and a transfer destination device each having a file to be synchronized with the file, wherein the transfer source device has data of the file at the transfer source to be synchronized with the file A first division unit that divides the block into a plurality of blocks, a first generation unit that generates a hash value from data included in each block divided by the first division unit, and the first generation unit A first transmission unit that transmits the hash value generated by the transfer destination device to the transfer destination device, wherein the transfer destination device stores the data of the file at the transfer destination that is a target of file synchronization as the first transmission unit. A second dividing unit that divides the blocks divided by the dividing unit into blocks of the same size, and data included in each block divided by the second dividing unit; A second generation unit that generates a hash value, a hash value generated by the first generation unit, and a hash value generated by the second generation unit, including generation data of each hash value A second transmission unit that compares each block number for identifying a block and transmits the block number corresponding to the hash value that does not match to the transfer source device, and the second number of the transfer source device 1. The file synchronization system according to claim 1, wherein the transmission unit 1 transmits data included in the block corresponding to the block number received from the transfer destination device to the transfer destination device.

  (Supplementary note 2) The file synchronization system according to supplementary note 1, wherein the file is a file storing a fixed-length record.

  (Supplementary Note 3) The file synchronization system according to Supplementary Note 1 or 2, wherein the file is a write-once file.

  (Supplementary note 4) A file synchronization method executed in a file synchronization system including a transfer source device and a transfer destination device each having a file to be synchronized with the file, wherein the transfer source device is a file synchronization target A first dividing step of dividing the original data of the file into a plurality of blocks; a first generating step of generating a hash value from the data included in each block divided in the first dividing step; A first transmission step of transmitting the hash value generated in the first generation step to the transfer destination device, wherein the transfer destination device is the data of the file at the transfer destination that is the target of file synchronization. A second dividing step of dividing the block into blocks of the same size as the blocks divided in the first dividing step; In the second generation step of generating a hash value from the data included in each block divided in the second division step, the hash value generated in the first generation step, and the second generation step, The generated hash value is compared for each block number identifying the block including the generation source data of each hash value, and the block number corresponding to the hash value that does not match is transmitted to the transfer source device. 2, and the first transmission step of the transfer source device transmits data included in the block corresponding to the block number received from the transfer destination device to the transfer destination device. A file synchronization method characterized by that.

  (Supplementary Note 5) A file synchronization program for causing a computer to execute each step described in Supplementary Note 4.

  DESCRIPTION OF SYMBOLS 1 ... File synchronization system, 10 ... Transfer origin apparatus, 11 ... Real data division part, 12 ... Hash value generation part, 13 ... Transmission part, 14 ... Memory | storage part, 15 ... Transfer selection part, 20 ... Transfer destination apparatus, 21 ... Real data division unit, 22 ... hash value generation unit, 23 ... transmission unit, 24 ... storage unit, 30 ... network, 141, 241 ... file.

Claims (5)

A file synchronization system comprising a transfer source device and a transfer destination device each having a file to be synchronized with a file,
The transfer source device
A first dividing unit that divides the data of the file that is the target of file synchronization into a plurality of blocks;
A first generator that generates a hash value from data included in each block divided by the first divider;
A first transmission unit that transmits the hash value generated by the first generation unit to the transfer destination device,
The transfer destination device is:
A second division unit that divides the data of the transfer destination file to be subjected to file synchronization into blocks of the same size as the blocks divided by the first division unit;
A second generation unit that generates a hash value from data included in each block divided by the second division unit;
The hash value generated by the first generation unit and the hash value generated by the second generation unit are respectively compared for each block number that identifies the block including the generation source data of each hash value. A second transmitter that transmits the block number corresponding to the hash value to the transfer source device,
The first transmission unit of the transfer source device transmits data included in the block corresponding to the block number received from the transfer destination device to the transfer destination device;
A file synchronization system characterized by that.   The file synchronization system according to claim 1, wherein the file is a file storing a fixed-length record.   3. The file synchronization system according to claim 1, wherein the file is a write-once file. A file synchronization method executed by a file synchronization system including a transfer source device and a transfer destination device each having a file to be synchronized with a file,
The transfer source device is
A first dividing step of dividing the data of the file of the transfer source subject to file synchronization into a plurality of blocks;
A first generation step of generating a hash value from data included in each block divided in the first division step;
Performing a first transmission step of transmitting the hash value generated in the first generation step to the transfer destination device;
The destination device is
A second division step of dividing the data of the file of the transfer destination to be subjected to file synchronization into blocks having the same size as the blocks divided in the first division step;
A second generation step of generating a hash value from data included in each block divided in the second division step;
The hash value generated in the first generation step and the hash value generated in the second generation step are respectively compared for each block number that identifies the block including the generation source data of each hash value. A second transmission step of transmitting the block number corresponding to the hash value to the transfer source device,
The first transmission step of the transfer source device transmits data included in the block corresponding to the block number received from the transfer destination device to the transfer destination device;
A file synchronization method characterized by the above.   A file synchronization program for causing a computer to execute each step according to claim 4.

Images