Edge server and storage control method

1. An edge server configured to perform overwrite preventive processing of a corresponding file in a core server, comprising:

a communication interface device which is configured to communicate with a core server; and

a processor which is connected to a memory and the communication interface device and configured to provide a first home directory and write a file in the first home directory according to a write request to the first home directory, wherein

the core server provides a core space,

the core space is a file system space to become a copy destination of updates of files and directories of each of the first home directory and a second home directory,

the first home directory is a first file system space used by a user,

the second home directory is a second file system space used by the user and provided by a separate edge server,

wherein a first file is a file in the first home directory that has been updated,

the preventive processing is executed by the processor and includes the processes of:

creating a first directory in the first home directory;

copying the first file to the first directory while maintaining a path structure of the first file;

copying the first directory to the core space as the process of copying the update of the first home directory to the core server;

creating a second directory in the first home directory;and

moving directories, excluding the second directory, and files belonging to a route directory of the first home directory to the second directory while maintaining the path structure,

wherein the first file copied to the first directory is a same file as a file in the files that have been moved to the second directory, and the path structure of the first file in the second directory is a same as the path structure in the first directory,

wherein the second file is a file that has been updated in the second home directory and copied to the core space, and

wherein the first file is a file that corresponds to the second file and has not been copied to the core space.

2. The edge server according to claim 1 , wherein the files copied to the first directory are all files that have been updated in the first home directory.

3. The edge server according to claim 2 , wherein the preventive processing further includes a process of copying, to the first home directory, at least a subordinate directory or a subordinate file of a route directory of the core space.

4. The edge server according to claim 2 , wherein the preventive processing includes a process of maintaining the inclusion of the update of the path structure of the first file in the update of the first home directory so that the updated path structure of the updated first file is added to the core space as the path structure to the second file based on the reflection of the update of the first home directory in the core space.

5. The edge server according to claim 2 , wherein

the preventive processing further includes the following process of overwriting the first file with the second file when the respective path structures of the first file and the second file are the same and the update time point of the first file is older than the update time point of the second file in the synchronization processing.

6. The edge server according to claim 1 , wherein

the preventive processing includes the process of:

determining whether one of an update time point of the first file and an update time point of the second file is older than the other; and

copying the first file to the first directory when the update time point of the first file is older than the update time point of the second file.

7. The edge server according to claim 6 , wherein the preventive processing further includes the following processes of:

reversing a directory structure of the first home directory to a directory structure prior to the update; and

identifying, after the reverse, the first file among the files that have been updated in the first home directory.

8. The edge server according to claim 6 , wherein

the preventive processing includes a process of creating, in a subordinate of the first home directory, a time stamp directory which is a directory that includes, as a directory name, a value indicating a creation time point of the first home directory or an update time point of the first file, and

the processor is configured to copy the first file to the subordinate of the time stamp directory in the preventive processing.

9. The edge server according to claim 6 , wherein the processor is configured to copy the update of the core space to the first home directory after the update of the first home directory is copied to the core server.

10. The edge server according to claim 1 , wherein

the preventive processing includes the following processes of:

synchronization processing of copying the update of the core space to the first home directory; and

copying the second file to the first home directory while maintaining a path structure of the second file in the core space and excluding the first file from the update of the first home directory when the respective path structures in the first file and the second file are different in the synchronization processing.