File handle banking to provide non-disruptive migration of files

• US 8,086,638 B1
• Filed: 03/31/2010
• Issued: 12/27/2011
• Est. Priority Date: 03/31/2010
• Status: Active Grant

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Hayden, John M., Stacey, Christopher H.
• Primary Examiner(s): Woo, Isaac M
• Application Number:
  US12/751,831
• Time in Patent Office: 636 Days
• Field of Search: 707600-831
• US Class Current: 707/791
• CPC Class Codes: G06F 16/119 Details of migration of file systems migration mechanisms in storage systems G06F3/0647

Abstract

When a directory tree is migrated from a source file system to a target file system, the directories of the directory tree are retained in the source file system, and handle translation entries are substituted for the regular data files of the directory tree in the source file system. The handle translation entries provide new file handles for the regular data files when the source file system is accessed with old file handles of the regular data files. For example, each handle translation entry includes the old file handle, a file system identifier, and the new file handle. The old file handle provides verification of the file handle being used for accessing the handle translation entry, and the file system identifier identifies the target file system in which the new file handle is valid.

Claims

1. In a data processing system including at least one client and at least one file server providing client access to regular data files in a directory tree in data storage by providing said at least one client with file handles that said at least one client includes in file access requests for access to the regular data files, a method of providing said at least one client with access to the regular data files concurrent with migration of the directory tree from a source file system to a target file system, the regular data files having respective old file handles in the source file system, and the regular data files having respective new file handles in the target file system, said method comprising:

upon migrating the directory tree from the source file system to the target file system, retaining directories of the directory tree in the source file system, and substituting handle translation entries for the regular data files in the source file system, the handle translation entries providing the respective new file handles for the regular data files, so that file access to the source file system using the old file handles provides access to the handle translation entries providing the respective new file handles for the regular data files; and

responding to a request from said at least one client for access to one of the regular data files by using the old file handle for said one of the regular data files for access to the source file system to access the handle translation entry for said one of the regular data files to obtain the new file handle for said one of the regular data files and using the new file handle for said one of the regular data files for accessing said one of the regular data files in the target file system.

2. The method as claimed in claim 1, wherein the handle translation entry for said each of the regular data files includes the old file handle for said each of the regular data files, a file system identifier identifying the target file system, and the new file handle for said each of the regular data files, and wherein the method further includes comparing a file handle in the request from said at least one client for access to said one of the regular data files to the old file handle included in the handle translation entry for said one of the regular data files to verify that the file handle in the request from said at least one client for access to said one of the regular data files is equal to the old file handle included in the handle translation entry for said one of the regular data files, and wherein the method further includes using the file system identifier identifying the target file system for accessing said one of the regular data files in the target file system.

3. The method as claimed in claim 1, which further includes removing the handle translation entries from the source file system when the handle translation entries have not been frequently accessed.

4. The method as claimed in claim 1, wherein each of the regular data files in the source file system includes an inode and file data, and wherein the method includes substituting the handle translation entry for said each of the regular data files by deleting the file data of said each of the regular data files from the source file system and inserting the handle translation entry for said each of the regular data files into the inode of said each of the regular data files.

5. The method as claimed in claim 4, wherein the inode of said each of the regular data files includes a flag indicating whether or not said each of the regular data files has been migrated, and the method includes inspecting the flag in the inode of said one of the regular data files in response to the request from said at least one client for access to said one of the regular data files, and in response to finding that the flag in the inode of said one of the regular data files indicates that said one of the regular data files has been migrated, accessing the handle translation entry in the inode of said one of the regular data files to obtain the new file handle for said one of the regular data files.

6. The method as claimed in claim 4, wherein the inode of said each of the regular data files has an attribute indicating a last access time, and wherein the method includes setting the last access time attribute of the inode when the handle translation entry for said each of the regular data files is inserted into the inode of said each of the regular data files, and re-setting the last access time attribute of the inode when the handle translation entry for said each of the regular data files is accessed for translation of the old file handle for said each of the regular data files into a new file handle for said each of the regular data files, and wherein the method includes reading the last access time attribute of the inode of said each of the regular data files in order to delete the inode of said each of the regular data files from the source file system when the handle translation entry for said each of the regular data files is infrequently accessed for translation of the old file handle for said each of the regular data files into a new file handle for said each of the regular data files.

7. The method as claimed in claim 1, wherein the method further includes responding to the migration of each directory in the directory tree from the source file system to the target file system by marking said each directory in the directory tree in the source file system to indicate that said each directory in the directory tree has been migrated from the source file system, and wherein the method includes responding to a request from said at least one client for access to one of the directories in the directory tree in the source file system by finding that said one of the directories in the directory tree in the source file system has been marked in the source file system to indicate that said one of the directories in the directory tree has been migrated from the source file system, and in response to finding that said one of the directories in the directory tree in the source file system has been marked in the source file system to indicate that said one of the directories in the directory tree in the source file system has been migrated from the source file system, denying access of said at least one client to said one of the directories in the directory tree in the source file system.

8. The method as claimed in claim 7, which further includes, in response to finding that said one of the directories in the directory tree in the source file system has been marked in the source file system to indicate that said one of the directories in the directory tree in the source file system has been migrated from the source file system, accessing a target path database to obtain information for directing access of said at least one client to said one of the directories in the directory tree in the target file system, and upon obtaining the information for directing access of said at least one client to said one of the directories in the directory tree in the target file system, directing access of said at least one client to said one of the directories in the directory tree in the target file system.

9. In a data processing system including at least one client, a source file server, and a target file server, the source file server providing client access to regular data files in a directory tree in data storage of the source file server by providing said at least one client with file handles that said at least one client includes in file access requests for access to the regular data files, a method of providing said at least one client with access to the regular data files concurrent with migration of the directory tree from the source file server to the target file server, the regular data files having respective old file handles in the source file server, and the regular data files having respective new file handles in the target file server, the target file server providing client access to the regular data files in the directory tree in data storage of the target file server in response to client requests for access to the regular data files in the target file server when the client requests for access to the regular data files in the target file server include the new file handles, said method comprising:

upon migrating the directory tree from the source file server to the target file server, retaining directories of the directory tree in the source file server, and substituting handle translation entries for the regular data files in the source file server, the handle translation entries providing the respective new file handles for the regular data files, so that file access to the source file server using the old file handles provides access to the handle translation entries providing the respective new file handles for the regular data files; and

responding to a request from said at least one client for access to one of the regular data files by using the old file handle for said one of the regular data files for access to the source file server to access the handle translation entry for said one of the regular data files to obtain the new file handle for said one of the regular data files and using the new file handle for said one of the regular data files for accessing said one of the regular data files in the target file server.

10. The method as claimed in claim 9, wherein the handle translation entry for said each of the regular data files includes the old file handle for said each of the regular data files, a file system identifier identifying the target file server, and the new file handle for said each of the regular data files, and wherein the method further includes comparing a file handle in the request from said at least one client for access to said one of the regular data files to the old file handle included in the handle translation entry for said one of the regular data files to verify that the file handle in the request from said at least one client for access to said one of the regular data files is equal to the old file handle included in the handle translation entry for said one of the regular data files, and wherein the method further includes using the file system identifier identifying the target file server for accessing said one of the regular data files in the target file server.

11. The method as claimed in claim 9, which further includes removing the handle translation entries from the source file server when the handle translation entries have not been frequently accessed.

12. The method as claimed in claim 9, wherein each of the regular data files in the source file server includes an inode and file data, and wherein the method includes substituting the handle translation entry for said each of the regular data files by deleting the file data of said each of the regular data files from the source file server and inserting the handle translation entry for said each of the regular data files into the inode of said each of the regular data files.

13. The method as claimed in claim 12, wherein the inode of said each of the regular data files includes a flag indicating whether or not said each of the regular data files has been migrated, and the method includes inspecting the flag in the inode of said one of the regular data files in response to the request from said at least one client for access to said one of the regular data files, and in response to finding that the flag in the inode of said one of the regular data files indicates that said one of the regular data files has been migrated, accessing the handle translation entry in the inode of said one of the regular data files to obtain the new file handle for said one of the regular data files.

14. The method as claimed in claim 12, wherein the inode of said each of the regular data files has an attribute indicating a last access time, and wherein the method includes setting the last access time attribute of the inode when the handle translation entry for said each of the regular data files is inserted into the inode of said each of the regular data files, and re-setting the last access time attribute of the inode when the handle translation entry for said each of the regular data files is accessed for translation of the old file handle for said each of the regular data files into a new file handle for said each of the regular data files, and wherein the method includes reading the last access time attribute of the inode of said each of the regular data files in order to delete the inode of said each of the regular data files from the source file server when the handle translation entry for said each of the regular data files is infrequently accessed for translation of the old file handle for said each of the regular data files into a new file handle for said each of the regular data files.

15. A file server comprising:

data storage for storing a directory tree in a source file system, the directory tree having a root directory and regular data files; and

at least one data processor coupled to the data storage and programmed for providing at least one client with access to the regular data files in the directory tree by providing said at least one client with file handles that said at least one client includes in file access requests for access to the regular data files,

wherein said at least one data processor is further programmed for providing said at least one client with access to the regular data files concurrent with migration of the directory tree from the source file system to a target file system, the regular data files having respective old file handles in the source file system, and the regular data files having respective new file handles in the target file system,

wherein said at least one data processor is programmed to migrate the directory tree from the source file system to the target file system while retaining directories of the directory tree in the source file system and substituting handle translation entries for the regular data files in the source file system, the handle translation entries providing the respective new file handles for the regular data files so that file access to the source file system using the old file handles provides access to the handle translation entries providing the respective new file handles for the regular data files; and

wherein said at least one data processor is programmed to respond to a request from said at least one client for access to one of the regular data files by using the old file handle for said one of the regular data files for access to the source file system to access the handle translation entry for said one of the regular data files to obtain the new file handle for said one of the regular data files so that the new file handle for said one of the regular data files is used for accessing said one of the regular data files in the target file system.

16. The file server as claimed in claim 15, wherein the handle translation entry for said each of the regular data files includes the old file handle for said each of the regular data files, a file system identifier identifying the target file system, and the new file handle for said each of the regular data files, and wherein said at least one data processor is further programmed to compare a file handle in the request from said at least one client for access to one of the regular data files to the old file handle included in the handle translation entry for said one of the regular data files to verify that the file handle in the request from said at least one client for access to said one of the regular data files is equal to the old file handle included in the handle translation entry for said one of the regular data files, and to use the file system identifier identifying the target file system for accessing said one of the regular data files in the target file system.

17. The file server as claimed in claim 15, wherein said at least one data processor is further programmed to remove the handle translation entries from the source file system when the handle translation entries have not been frequently accessed.

18. The file server as claimed in claim 15, wherein each of the regular data files in the source file system includes an inode and file data, and wherein said at least one data processor is programmed to substitute the handle translation entry for said each of the regular data files by deleting the file data of said each of the regular data files from the source file system and inserting the handle translation entry for said each of the regular data files into the inode of said each of the regular data files.

19. The file server as claimed in claim 18, wherein the inode of said each of the regular data files includes a flag indicating whether or not said each of the regular data files has been migrated, and wherein said at least one data processor is further programmed to inspect the flag in the inode of said one of the regular data files in response to the request from said at least one of the client for access to said one of the regular data files, and in response to finding that the flag in the inode of said one of the regular data files indicates that said one of the regular data files has been migrated, to access the handle translation entry in the inode of said one of the regular data files to obtain the new file handle for said one of the regular data files.

20. The file server as claimed in claim 18, wherein the inode of said each of the regular data files has an attribute indicating a last access time, and said at least one data processor is further programmed to set the last access time attribute of the inode when the handle translation entry for said each of the regular data files is inserted into the inode of said each of the regular data files, and to reset the last access time attribute of the inode when the handle translation entry for said each of the regular data files is accessed for translation of the old file handle for said each of the regular data files into a new file handle for said each of the regular data files, and wherein said at least one data processor is further programmed to read the last access time attribute of the inode of said each of the regular data files in order to delete the inode of said each of the regular data files from the source file system when the handle translation entry for said each of the regular data files is infrequently accessed for translation of the old file handle for said each of the regular data files into a new file handle for said each of the regular data files.