Client-server protocol for directory access of snapshot file systems in a storage system

• US 7,284,016 B2
• Filed: 12/03/2002
• Issued: 10/16/2007
• Est. Priority Date: 12/03/2002
• Status: Active Grant

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Zheng, Jiannan, Jiang, Xiaoye, Venkatesh, Dinesh, Vahalia, Uresh
• Primary Examiner(s): Wong; Don
• Assistant Examiner(s): Le; Michael
• Application Number:
  US10/308,445
• Publication Number:
  US 20040107222A1
• Time in Patent Office: 1,778 Days
• Field of Search: 707/200, 707/202, 707/204, 711/202
• US Class Current: 1/1
• CPC Class Codes: G06F 11/1435 using file system or storage system metadata
• CPC Class Codes: G06F 16/10 File systems; File servers
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

Internally, a production file system and each of its related snapshot file systems have a common file system identifier (fid′) and a unique respective file system identifier (fsid′). Externally, the production file system and each of its related snapshot file systems has a common file system identifier (fsid) and a unique respective file identifier (fid). For example, the “fsid” and “fid” for the production and snapshot file systems are interchanged between a client-server protocol layer and a logical volume layer in a file server. Moreover, the file handle for an object indicates whether an object is in either a production file system that is not configured to have related snapshots, a production file system that is configured to have related snapshots, or a snapshot file system. When the object is in a snapshot file system, the file handle also indicates the related production file system.

Claims

1. A computer-implemented method of accessing a group of related snapshot file systems stored in an electronic data storage system, each of the related snapshot file systems being the state of a production file system at a respective point in time, each of the related snapshot file systems having been configured to have a common internal file identifier (fid′

) and a different respective internal file system identifier (fsid′

), wherein said computer-implemented method comprises;

decoding a pathname to an object in one of the related snapshot file systems in accordance with a file access protocol, the decoding of the pathname to the object selecting a common external file system identifier (fsid) for the group of related snapshot file systems, the common external file system identifier (fsid) for the group of related snapshot file systems being the common internal file identifier (fid′

), and selecting a respective external file identifier (fid) distinguishing said one of the related snapshot file systems from the other related snapshot file systems in the group of related snapshot file systems, and selecting a file identifier for the object within said one of the related snapshot file systems; and

accessing the object in said one of the related snapshot file systems by using the common external file system identifier (fsid) for the group of related snapshot file systems to select the group of related snapshot file systems from within the electronic data storage system, using the external file identifier (fid) distinguishing said one of the related snapshot file systems from the other related snapshot file systems in the group of related snapshot file systems as the internal file system identifier (fsid′

) to select said one of the related snapshot file systems stored in the electronic data storage system from within the selected group of related snapshot file systems, and using the file identifier for the object within said one of the related snapshot file systems to select and access the object from within said one of the related snapshot file systems.

2. The computer-implemented method as claimed in claim 1, wherein the production file system is stored in the electronic data storage system, the production file system has been configured to have the common internal file identifier (fid′

) and an internal file system identifier (fsid′

), and wherein said method further includes;

decoding a pathname to the object in the production file system in accordance with the file access protocol, the decoding of the pathname to the object selecting the common external file system identifier (fsid) for the group of related snapshot file systems, and selecting an external file identifier (fid) distinguishing the production file system from the related snapshot file systems in the group of related snapshot file systems, and selecting a file identifier for the object within the production file system; and

accessing the object in the production file system by using the common external file system identifier (fsid) for the group of related snapshot file systems to select the group of related snapshot file systems from within the electronic data storage system, using the external file identifier (fid) distinguishing the production file system from the related snapshot file systems in the group of related snapshot file systems as the respective internal file system identifier (fsid′

) to select the production file system stored in the electronic data storage system from within the selected group of related snapshot file systems, and using the file identifier for the object within the production file system to select and access the object from within the production file system.

3. The computer-implemented method as claimed in claim 1, wherein the decoding of the pathname is performed in a client-server protocol that produces a file handle indicating a location for the object in said one of the related snapshot file systems in the electronic data storage system, and the accessing of the object is performed in the client-server protocol by using the file handle for locating the object in said one of the related snapshot file systems in the electronic data storage system.

4. The computer-implemented method as claimed in claim 3, wherein the client-server protocol is the Network File System (NFS) client-server protocol.

5. The computer-implemented method as claimed in claim 3, wherein the file handle indicating the location for the object in said one of the related snapshot file systems in the electronic data storage system includes the common external file system identifier (fsid) for the group of related snapshot file systems, the respective external file identifier (fid) distinguishing said one of the related snapshot file systems from the other related snapshot file systems in the group of related snapshot file systems, and the file identifier for the object within said one of the related snapshot file systems.

6. The computer-implemented method as claimed in claim 5, wherein the production file system is also stored in the electronic data storage system, and wherein the file handle indicating the location for the object in said one of the related snapshot file systems in the electronic data storage system further includes a respective external file identifier (fid) distinguishing the production file system from the related snapshot file systems in the group of related snapshot file systems.

7. The computer-implemented method as claimed in claim 3, which includes encoding in the file handle an indication of whether the object is located in either a file system that is not configured to have related snapshot file systems, a production file system configured to have related snapshot file systems, or a snapshot file system.

8. The computer-implemented method as claimed in claim 1, wherein the electronic data storage system is a network file server, the method includes performing a client-server protocol for file access, the client-server protocol is performed by a client-server protocol layer of programming of the network file server, and the method includes interchanging file system identifiers and file identifiers of the related snapshot file systems as the file system identifiers and file identifiers are passed between the client-server protocol layer of programming and the related snapshot file systems.

9. The computer-implemented method as claimed in claim 1, which includes initially configuring each of the related snapshot file systems to have a common internal file identifier (fid′

) and a different respective internal file system identifier (fsid′

).

10. The computer-implemented method as claimed in claim 1, wherein the electronic data storage system is a network file server, and the method includes re-programming a client-server protocol layer for the network file server to interchange file system identifiers and file identifiers for the related snapshot file systems.

11. A method of configuring a network file server for access to a group of related snapshot file systems in data storage of the network file server, each of the related snapshot file systems being the state of a production file system at a respective point in time, the network file server having a client-server protocol layer of programming for client access to file system objects in the data storage of the network file server, said method comprising:

configuring each of the related snapshot file systems to have a common internal file identifier (fid′

) and a different respective internal file system identifier (fsid′

); and

programming the network file server for interchanging the common internal file identifier (fid′

) with the different respective internal file system identifier (fsid′

) of each related snapshot file system for access using the client-server protocol layer to said each related snapshot file system.

12. The method as claimed in claim 11, wherein the production file system is stored in the data storage of the network file server, and wherein the method further includes:

configuring the production file system to have the common internal file identifier (fid′

) and an internal file system identifier (fsid′

), and

programming the network file server for interchanging the common internal file identifier (fid′

) with the internal file system identifier (fsid′

) of the production file system for access of the client-server protocol layer to the production file system in the data storage of the network file server.

13. The method as claimed in claim 11, wherein the client-server protocol layer responds to a directory lookup request from a client by returning to the client a file handle pointing to a file system object in the data storage of the network file server, and wherein the method further includes programming the client-server protocol layer to encode, in the file handle, an indication of whether the object is located in either a file system that is not configured to have related snapshot file systems, a production file system configured to have related snapshot file systems, or a snapshot file system.

14. The method as claimed in claim 11, wherein the client-server protocol layer responds to a directory lookup request from a client to produce and return to the client a file handle pointing to a file system object in one of the related snapshot file systems in the data storage of the network file server, and wherein the method further includes programming the client-server protocol layer to encode, in the file handle, a mount handle indicating where the group of related snapshot file systems is mounted in the data storage of the network file server, a file identifier indicating where said one of the related snapshot file systems is located within the group of related snapshot file systems, and a file identifier indicating where the file system object is located within said one of the related snapshot file systems.

15. The method as claimed in claim 11, wherein the production file system is stored in the data storage of the network file server, the client-server protocol layer responds to a directory lookup request from a client for access to a file system object in one of the related snapshot file systems by returning to the client a file handle pointing to the file system object in said one of the related snapshot file systems, and wherein the method further includes programming the client-server protocol layer to encode, in the file handle, a file identifier indicating where the production file system is located in the data storage of the network file server, a file identifier indicating where said one of the related snapshot file systems is located in the data storage of the network file server, and a file identifier indicating where the file system object is located within said one of the related snapshot file systems.

16. A method of configuring a network file server for access to a group of related snapshot file systems in data storage of the network file server, each of the related snapshot file systems being the state of a production file system at a respective point in time, the network file server having a client-server protocol layer of programming for client access to file system objects in the data storage of the network file server, said method comprising:

configuring each of the related snapshot file systems to have a common internal file identifier (fid′

) and a different respective internal file system identifier (fsid′

); and

programming the network file server for interchanging the common internal file identifier (fid′

) with the internal file system identifier (fsid′

) of each related snapshot file system for access of the client-server protocol layer to said each related snapshot file system.

17. The method as claimed in claim 16, wherein the production file system is stored in the data storage of the network file server, and wherein the method further includes:

configuring the production file system to have the common internal file identifier (fid′

) and an internal file system identifier (fsid′

), and

programming the network file server for interchanging the common internal file identifier (fid′

) with the internal file system identifier (fsid′

) of the production file system for access of the client-server protocol layer to the production file system.

18. The method as claimed in claim 16, wherein the client-server protocol responds to a directory lookup request from a client to produce and return to the client a file handle pointing to a file system object in the data storage of the network file server, and wherein the method further includes programming the client-server protocol layer to encode, in the file handle, an indication of whether the object is located in either a file system that is not configured to have related snapshot file systems, a production file system configured to have related snapshot file systems, or a snapshot file system.

19. The method as claimed in claim 16, wherein the client-server protocol responds to a directory lookup request from a client by returning to the client a file handle pointing to a file system object in one of the related snapshot file systems in the data storage of the network file server, and wherein the method further includes programming the client-server protocol layer to encode, in the file handle, a mount handle indicating where the group of related snapshot file systems is mounted in the data storage of the network file server, a file identifier indicating where said one of the related snapshot file systems is located within the group of related snapshot file systems, and a file identifier indicating where the file system object is located within said one of the related snapshot file systems.

20. A method of operating a network file server having data storage storing a production file system and related snapshot file systems, each of the related snapshot file systems being the state of the production file system at a respective point in time, wherein the method comprises:

responding to a directory lookup request from a client for access to a file system object in one of the related snapshot file systems by returning to the client a file handle pointing to the file system object in said one of the related snapshot file systems, and

responding to an access request including the file handle by decoding the file handle to locate and access the object in said one of the related snapshot file systems;

which includes encoding in the file handle a file identifier indicating where the production file system is located in the data storage of the network file server, a file identifier indicating where said one of the related snapshot file systems is located in the data storage of the network file server, and a file identifier indicating where the file system object is located within said one of the related snapshot file systems.

21. The method as claimed in claim 20, wherein the production file system and the related snapshot file systems are included in a parent file system, and wherein the method further includes encoding in the file handle a file system identifier of the parent file system.

22. A method of operating a network file server having data storage storing a production file system and related snapshot file systems, each of the related snapshot file systems being the state of the production file system at a respective point in time, wherein the method comprises:

responding to a directory lookup request from a client for access to a file system object in the data storage of the network file server by returning to the client a file handle pointing to the file system object in the data storage of the network file server, and

responding to an access request including the file handle by decoding the file handle to locate and access the object in the data storage of the network file server,

which includes encoding in the file handle an indication of whether the file system object is in either a file system that is not configured for having related snapshot file systems, a production file system that is configured for having related snapshot file systems, or a snapshot file system,

wherein the production file system and the related snapshot file systems are included in a parent file system, and wherein the method further includes encoding in the file handle a file system identifier of the parent file system.

23. The method as claimed in claim 22, wherein the object is in one of the related snapshot file systems, and the file handle includes a file identifier indicating where the production file system is found in the data storage of the network file server, a file identifier indicating where said one of the related snapshot file systems is located in the data storage of the network file server, and a file identifier indicating where the object is located in said one of the related snapshot file systems.

24. The method as claimed in claim 22, wherein the object is in the production file system, the file handle includes a file identifier indicating where the object is located in the production file system, and the file handle includes two instances of a file identifier indicating where the production file system is found in the data storage of the network file server.

25. The method as claimed in claim 22, wherein the file handle includes a first sub-block that includes a file identifier of the production file system if the object is not in a file system that is not configured for having related snapshots, a second sub-block that includes a file system identifier of a file system including the object if the object is in a file system that is not configured for having related snapshots or otherwise the second sub-block includes a file system identifier of the parent file system, a third sub-block that includes the file identifier of the production file system if the object is in the production file system or that includes the file identifier of one of the related snapshot file systems if the object is in one of the related snapshot file systems, and a fourth sub-block that includes an identifier indicating where the object is located in the file system that is not configured for having related snapshots, in the production file system, or in said one of the related snapshot file systems.

26. A network file server comprising:

data storage for storing a production file system and a group of related snapshot file systems, each of the related snapshot file systems being the state of the production file system at a respective point in time; and

a client-server protocol layer of programming for client access to file system objects in the data storage of the network file server;

wherein each of the related snapshot file systems has a common internal file identifier (fid′

) and a different respective internal file system identifier (fsid′

); and

wherein the network file server is programmed for interchanging the common internal file identifier (fid′

) with the respective internal file system identifier (fsid′

) of each related snapshot file system for access of the client-server protocol layer to said each related snapshot file system.

27. The network file server as claimed in claim 26, wherein the production file system has the common internal file identifier (fid′

) and an internal file system identifier (fsid′

), and the network file server is programmed for interchanging the common internal file identifier (fid′

) with the internal file system identifier (fsid′

) of the production file system for access of the client-server protocol layer to the production file system.

28. The network file server as claimed in claim 26, wherein the client-server protocol responds to a directory lookup request from a client to produce and return to the client a file handle pointing to a file system object in the data storage of the network file server, and

wherein the client-server protocol layer encodes, in the file handle, an indication of whether the object is located in either a file system that is not configured to have related snapshot file systems, a production file system configured to have related snapshot file systems, or a snapshot file system.

29. The network file server as claimed in claim 28, which includes decoding and comparing sub-blocks of the file handle to determine whether the object is in either a file system that is not configured for having related snapshot file systems, a production file system that is configured for having related snapshot file systems, or a snapshot file system.

30. The network file server as claimed in claim 29, wherein the mount handle includes a file system identifier identifying a file system including the production file system and the related snapshot file systems, and a file identifier of the production file system.

31. The network file server as claimed in claim 28, wherein the client-server protocol layer decodes the file handle returned from the client to determine whether to invoke a first routine for accessing a file system that is not configured for having related snapshot file systems, a second routine for accessing a production file system that is configured for having related snapshot file systems, or a third routine for accessing a snapshot file system.

32. The network file server as claimed in claim 26, wherein the client-server protocol layer responds to a directory lookup request from a client by returning to the client a file handle pointing to a file system object in one of the related snapshot file systems, and wherein the client-server protocol layer encodes, in the file handle, a mount handle indicating where the group of related snapshot file systems is mounted in the data storage, a file identifier indicating where said one of the related snapshot file systems is located within the group of related snapshot file systems, and a file identifier indicating where the object is located within said one of the related snapshot file systems.

33. A network file server comprising:

data storage for storing a production file system and a group of related snapshot file systems, each of the related snapshot file systems being the state of the production file system at a respective point in time; and

a client-server protocol layer of programming for client access to file system objects in the data storage of the network file server;

wherein the client-server protocol layer responds to a directory lookup request from a client for access to a file system object in one of the related snapshot file systems by returning to the client a file handle pointing to the file system object in said one of the related snapshot file systems, and

the client-server protocol layer responds to an access request from the client, the access request including the file handle, the client-server protocol layer responding by decoding the file handle to locate and access the object in said one of the related snapshot file systems;

wherein the client-server protocol layer encodes in the file handle a file identifier indicating where the production file system is located in the data storage of the network file server, a file identifier indicating where said one of the related snapshot file systems is located in the data storage of the network file server, and a file identifier indicating where the file system object is located within said one of the related snapshot file systems.

34. The network file server as claimed in claim 33, wherein the production file system and the related snapshot file systems are included in a parent file system, and wherein the client-server protocol layer includes in the file handle a file system identifier of the parent file system.

35. A network file server comprising:

data storage for storing a production file system and a group of related snapshot file systems, each of the related snapshot file systems being the state of the production file system at a respective point in time; and

a client-server protocol layer of programming for client access to file system objects in the data storage of the network file server;

wherein the client-server protocol layer responds to a directory lookup request from a client for access to a file system object in the data storage by returning to the client a file handle pointing to the file system object in the data storage, and

the client-server protocol layer responds to an access request from the client, the access request including the file handle, the client-server protocol layer responding to the access request by decoding the file handle to locate and access the object in the data storage,

wherein the client-server protocol layer encodes in the file handle an indication of whether the file system object is in either a file system that is not configured for having related snapshot file systems, a production file system that is configured for having related snapshot file systems, or a snapshot file system.

36. The network file server as claimed in claim 35, wherein the object is in one of the related snapshot file systems, and the file handle includes a file identifier indicating where the production file system is found in the data storage of the network file server, a file identifier indicating where said one of the related snapshot file systems is located in the data storage of the network file server, and a file identifier indicating where the object is located in said one of the related snapshot file systems.

37. The network file server as claimed in claim 35, wherein the object is in the production file system, the file handle includes a file identifier indicating where the object is located in the production file system, and the file handle includes two instances of a file identifier indicating where the production file system is found in the data storage of the network file server.

38. The network file server as claimed in claim 35, wherein the client-server protocol layer decodes and compares sub-blocks of the file handle to determine whether the file system object is in either a file system that is not configured for having related snapshot file systems, a production file system that is configured for having related snapshot file systems, or a snapshot file system.

39. The network file server as claimed in claim 38, wherein the network file server is programmed with a first file access routine for accessing a file in a file system that is not configured for having related snapshot file systems, a second file access routine for accessing a file in a production file system that is configured for having related snapshot file systems, and a third file access routine for accessing a file in a snapshot file system.

40. The network file server as claimed in claim 35, wherein the production file system and the related snapshot file systems are included in a parent file system, and wherein the client-server protocol layer encodes in the file handle a file system identifier of the parent file system.

41. The network file server as claimed in claim 40, wherein the file handle includes a first sub-block that includes a file identifier of the production file system if the object is not in a file system that is not configured for having snapshots, a second sub-block that includes a file system identifier if the object is in a file system that is not configured for having snapshots or otherwise includes a file system identifier of the parent file system, a third sub-block that includes the file identifier of the production file system if the object is in the production file system or that includes the file identifier of one of the related snapshot file systems if the object is in one of the related snapshot file systems, and a fourth sub-block that includes an identifier indicating where the object is located in the file system that is not configured for having related snapshots, in the production file system, or in said one of the related snapshot file systems.