Network file server sharing local caches of file access information in data processors assigned to respective file systems

• US 6,192,408 B1
• Filed: 09/26/1997
• Issued: 02/20/2001
• Est. Priority Date: 09/26/1997
• Status: Expired due to Term

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Vahalia, Uresh K., Tzelnic, Percy, Gupta, Uday, Porat, Betti
• Primary Examiner(s): Rinehart, Mark
• Assistant Examiner(s): Cardone, Jason D.
• Application Number:
  US08/938,723
• Time in Patent Office: 1,243 Days
• Field of Search: 709/208, 709/210, 709/217, 709/229, 709/201, 709/102, 709/105, 709/226, 707/10, 707/8, 710/110, 710/200, 711/147, 340/825.34, 712/32, 712/33, 395/874, 395/819
• US Class Current: 709/229
• CPC Class Codes: G06F 16/1774 Locking methods, e.g. locking methods for file systems allowing shared and concurrent access to files

Abstract

A network file server includes a first set of data processors for receiving requests from clients, and a second set of data processors for accessing read-write file systems. A respective data processor in the second set is assigned to each file system for exclusive management of read and write locks on the file system. Each data processor in the first set can authorize access to file systems directly accessed by more than one data processor in the second set. Processing of a request for access that is authorized is continued by the data processor that is assigned to manage the locks on the file system to be accessed. The exclusivity of lock management eliminates cache coherency problems, and dynamic load balancing can be used to prevent the lock management from becoming a bottleneck to performance. A preferred embodiment includes a cached disk storage subsystem linked to data mover computers. Each data mover has authorization and ownership information for a plurality of file systems, and maintains a local cache of locking information for file systems that the data mover can directly access. The data mover receives a client request, and if access is authorized, checks whether it can directly access the file, and if not, forwards the request to another data mover.

Claims

1. In a data network having clients and a network file server having an array of data processors receiving client requests for access to a plurality of read-write file systems wherein a respective one of the data processors is presently assigned to manage locks on each of the read-write file systems, a method used when any one of the data processors receives a client request for access to any one of the read-write file systems, the client request specifying said one of the read-write file systems to access, said method comprising the steps of:

a) in response to said one of the data processors receiving the client request, accessing stored assignment information indicating the respective one of the data processors being presently assigned to manage locks on said one of the file systems; and

b) forwarding the client request from the data processor initially receiving the client request to the data processor indicated by the stored assignment information as being presently assigned to manage locks on said one of the file systems; and

c) the respective one of the data processors indicated by the stored assignment information as being presently assigned to manage locks on said one of the file systems receiving the client request and continuing the processing of the client request by performing lock management for said one of the file systems for access to said one of the file systems as requested by the client request.

2. The method as claimed in claim 1, which includes, during processing of a client request for access to a file system, changing an assignment of lock management of the file system from a first data processor to a second data processor.

3. The method as claimed in claim 2, wherein processing of a client request for access to the file system is temporarily suspended during the changing of an assignment of lock management of the file system.

4. The method as claimed in claim 3, wherein processing of the client request for access to the file system is temporarily suspended upon looking up stored assignment information indicating that a reassignment of a data processor to manage locks on the file system is in progress, and processing of the client request is continued by the second data processor.

5. The method as claimed in claim 2, wherein the changing of the assignment of lock management of the file system is performed in response to a high loading condition of the first data processor.

6. The method as claimed in claim 2, wherein the changing of the assignment of lock management of the file system is performed in response to monitoring loading on the data processors and finding that loading on the first data processor is relatively high and loading on the second data processor is relatively low.

7. The method as claimed in claim 2, wherein the changing of the assignment of lock management of the file system includes transferring lock information for the file system from the first data processor to the second data processor.

8. The method as claimed in claim 1, which includes said data processor initially receiving the data request forwarding the client request over the network to the data processor indicated by the stored assignment information as being presently assigned to manage locks on said one of the file systems.

9. The method as claimed in claim 8, which includes the data processor indicated by the stored assignment information as being presently assigned to manage locks on said one of the file systems returning a response to the client request over the network to said data processor initially receiving said client request which transmits the response to the client request to a client having originated the client request.

10. The method as claimed in claim 1, which further includes the data processor initially receiving the client request decoding the request and accessing stored client information to authenticate the request before the continuing of processing of the request by the respective one of the data processors indicated by the stored assignment information as being presently assigned to manage locks on said one of the file systems.

11. The method as claimed in claim 1, which further includes the data processor initially receiving the client request accessing stored file system information to determine access authority required for performing the access to said one of the file systems as requested by the client request and determining that the client request has the access authority required for performing the access to said one of the file systems as requested by the client request before the continuing of processing of the client request by forwarding the client request to the data processor indicated by the stored assignment information as being presently assigned to manage locks on said one of the file systems.

12. The method as claimed in claim 1 wherein, after the data processor initially receives the client request forwards the client request to the data processor indicated by the stored assignment information as being presently assigned to manage locks on said one of the file systems, said lock managing data processor returns a response to the client request to said data processor initially receiving the client request which transmits the response to the client having originated the client request.

13. The method as claimed in claim 1, wherein the the data processor indicated by the stored assignment information as being presently assigned to manage locks on said one of the file systems continues the processing of the client request by accessing a file system cache of file data and file attributes for access to said one of the file systems as requested by the client request.

14. The method as claimed in claim 1, wherein the data processor indicated by the stored assignment information as being presently assigned to manage locks on said one of the file systems continues the processing of the client request by accessing said one of the file systems in disk storage of the data processor indicated by the stored assignment information as being presently assigned to manage locks on said one of the file systems.

15. The method as claimed in claim 1, wherein the data processor indicated by the stored assignment information as being presently assigned to manage locks on said one of the file systems continues the processing of the client request by accessing said one of the file systems in disk storage of a cached disk storage subsystem storing all of the plurality of read-write file systems.

16. A method of servicing a request from a client in a data network including a network server with an array of data processors for access to a read-write file, said method comprising the steps of:

a) one of the data processors in the array receiving the request;

decoding the request to identify the client and a requested data access operation and a file system to which access is requested;

accessing stored authorization information to obtain access requirements for the requested data access upon the file system; and

rejecting the request if access rights of the client do not satisfy the access requirements for the requested data access upon the file system, and if the access rights of the client satisfy the access requirements for the requested data access upon the file system, initiating continued processing for the request by another data processor in the array indicated by stored assignment information as presently assigned to access the file system;

b) the data processor indicated by the stored assignment information as presently assigned to access the file system accessing stored locking information indicating whether or not the requested data access operation by the client would be inconsistent with any pending data access operation upon the filing system; and

if the requested data access operation by the client would be inconsistent with a pending data access operation upon the file system, suspending the processing of the request, and if the requested data access operation by the client would not be inconsistent with any pending data access operation upon the file system, performing the requested data access operation upon the file system.

17. The method as claimed in claim 16, which includes, during the processing of the request, changing the stored assignment information from an indication that a first data processor is assigned to access the file system to an indication that a second data processor is assigned to access the file system.

18. The method as claimed in claim 17, wherein the changing of the stored assignment information includes storing an indication that a change is being made in the assignment of the data processor to access the file system, and suspending processing of the request during a period of time in which there is an indication that a change is being made in the assignment of the data processor to access the file system.

19. The method as claimed in claim 18, wherein processing of a client request for access to the file system is temporarily suspended after the data processor having received the request determines that the access rights of the client satisfy the access requirements for the requested data access upon the file system, and when the data processor having received the request looks up the stored assignment information to determine the data processor which is to continue processing of the request and finds that a change is in progress.

20. The method as claimed in claim 18, wherein write-pending locking information for the file system in a cache of file access information is transferred from memory of the first data processor to memory of the second data processor when there is an indication that a change is being made in the assignment of the data processor to access the file system.

21. The method as claimed in claim 18, wherein write-pending file attributes and data for the file system is transferred from memory of the first data processor to memory of the second data processor when there is an indication that a change is being made in the assignment of the data processor to access the file system.

22. The method as claimed in claim 18, wherein the file system is copied from disk storage of the first data processor to disk storage of the second data processor when there is an indication that a change is being made in the assignment of the data processor to access the file system.

23. The method as claimed in claim 17, wherein the changing of the stored assignment information is performed in response to a high loading condition of the first data processor.

24. The method as claimed in claim 17, wherein the changing of the stored assignment information is performed in response to monitoring loading on the first and second data processors and finding that loading on the first data processor is relatively high and loading on the second data processor is relatively low.

25. The method as claimed in claim 16, wherein the data processor having received the request is different from the data processor indicated by the stored assignment information as presently assigned to access the file system, and the data processor having received the request forwards the request over the network for continued processing by the data processor indicated by the stored assignment information as presently assigned to access the file system.

26. The method as claimed in claim 25, wherein the data processor indicated by the stored assignment information as presently assigned to access the file system returns a response over the network to the data processor having received the request, and the data processor having received the request forwards the response to the client.

27. The method as claimed in claim 16, wherein the data processor indicated by the stored assignment information as presently assigned to access the file system accesses the file system for all client requests for access to files in the file system, including client requests received by a plurality of data processors in the network, unless and until there is a change in the stored assignment information.

28. The method as claimed in claim 16, which includes the data processor having received the request checking whether the data processor indicated by the stored assignment information as presently assigned to access the file system is different from the data processor having received the request, and when the data processor indicated by the stored assignment information as presently assigned to access the file system is different from the data processor having received the request, transmitting the request to the data processor indicated by the stored assignment information as presently assigned to access the file system.

29. The method as claimed in claim 16, wherein the data processor indicated by the stored assignment information as presently assigned to access the file system returns a response to the data processor having received the request, and the data processor having received the request forwards the response to the client.

30. The method as claimed in claim 16, wherein the data processor indicated by the stored assignment information as presently assigned to access the file system has a file system cache of file data and file attributes and performs the requested data access operation upon the file system by accessing the file system cache.

31. The method as claimed in claim 16, wherein the data processor indicated by the stored assignment information as presently assigned to access the file system has disk storage and performs the requested data access operation upon the file system by accessing the disk storage.

32. In a network file server having a plurality of data processors, a method employed by a file system service for responding to a request from a client on the network for access to a file in a file system, said method comprising the steps of:

a) a data processor on the network receiving the request; and

b) decoding the request, checking client authorization for access to the file in the file system, and checking whether the file is in a remote file system, and

exporting the request to the remote file system when the file is in a remote file system, and

when the file is not in a remote file system, forwarding the request for further processing by a data processor assigned to manage access to the file system, and the data processor assigned to manage access to the file system verifying that the file system is exported to the client, and then processing the request and sending a reply to the client, wherein the data processor having received the request in step a) accesses stored information indicating associations between file systems and a respective one of the data processors assigned to manage access to each of the file systems in order to find the data processor assigned to manage access to the file system including the file to be accessed and to forward the request for further processing by the data processor assigned to manage access to the file system including the file to be accessed.

33. The method as claimed in claim 32, wherein the data processor having received the request in step a) forwards the request for further processing by the data processor assigned to manage access to the file system including the file to be accessed by checking whether the data processor assigned to manage access to the file system including the file to be accessed is the same as the data processor having received the request in step a), and if the data processor assigned to manage access to the file system including the file to be accessed is not the same as the data processor having received the request in step a), transmitting the request to the data processor assigned to manage access to the file system including the file to be accessed.

34. The method as claimed in claim 33, wherein the request is transmitted from the data processor having received the request in step a) to the data processor assigned to manage access to the file system by transmitting the request over the network.

35. The method as claimed in claim 33, wherein the request is transmitted from the data processor having received the request in step a) to the data processor assigned to manage access to the file system including the file to be accessed by transmitting the request over a dedicated data link isolated from the net work and linking the data processor having received the request in step a) to the data processor assigned to manage access to the file system including the file to be accessed.

36. The method as claimed in claim 32, which further includes monitoring loading on the data processor assigned to manage access to the file system, and changing the assignment of the data processor assigned to manage access to the file system from a first data processor to a second data processor when loading on the first data processor is relatively high in comparison to loading on the second data processor.

37. The method as claimed in claim 36, which further includes temporarily suspending processing of the request during a transfer of file access information for the file system from the first data processor to the second data processor when changing the assignment of the data processor assigned to manage access to the file system from the first data processor to the second data processor.

38. The method as claimed in claim 36, wherein the data processor assigned to manage access to the file system including the file to be accessed also manages a file system cache of file data and file attributes for files in the file system, and processing of the request is temporarily suspended during a transfer of write-pending file data and file attributes from the first data processor to the second data processor when changing the assignment of the data processor assigned to manage access to the file system from the first data processor to the second data processor.

39. The method as claimed in claim 32, wherein the file system service is a version of the Network File System (NFS).

40. The method as claimed in claim 32, wherein the data processor having originally received the request transmits the request to the data processor assigned to manage access to the file system, the data processor assigned to manage access to the file system transmits the reply to the data processor having originally received the request, and then the data processor having originally received the request forwards the reply to the client.

41. The method as claimed in claim 32, wherein the data processor assigned to manage access to the file system including the file to be accessed also processes any client request to create a new file in the file system.

42. The method as claimed in claim 32, wherein the data processor assigned to manage access to the file system including the file to be accessed manages read and write locks on files in the file system.

43. A network file server for providing clients with read-write access to read-write file systems, said network file server comprising, in combination:

a plurality of data processors, each of the data processors having a network interface for receiving requests from clients on a network, each of the data processors being assigned to access at least one of the read-write file systems, an assigned one of the data processors being programmed to perform access to each of the read-write file systems, wherein

each of the data processor is programmed to respond to a request by a client on the network for access to any one of the read-write file systems by decoding the request to identify the client and a requested data access operation and a file system to which access is requested;

accessing stored assignment information about clients and about file systems to obtain access rights of the client and access requirements for the requested data access upon the file system; and

rejecting the request if the access rights of the client do not satisfy the access requirements for the requested data access upon the file system, and if the access rights of the client satisfy the access requirements for the requested data access upon the file system, accessing stored assignment information indicating the assigned one of the data processors presently assigned to access the file system, and initiating continued processing for the client request by the assigned one of the data processors indicated by the stored assignment information as being presently assigned to access the file system; and

each of the data processors is programmed to respond to initiation of continued processing for access to a file system to which said each data processor is presently assigned to access by accessing stored locking information indicating whether or not the access of the continued processing would be inconsistent with any pending data access operation upon the file system to which said each data processor is presently assigned to access; and

if the access of the continued processing would be inconsistent with a pending data access operation upon the file system to which said each data processor is presently assigned to access, suspending the continued processing, and if the access of the continued processing would not be inconsistent with any pending data access operation upon the file system to which said each data processor is presently assigned to access, performing the access of the continued processing upon the file system.

44. The network file server as claimed in claim 43, which includes at least one data processor programmed to monitor loading on a first data processor for changing to a second data processor the assignment of data access to a read-write file system to which the first data processor is presently assigned to access.

45. The network file server as claimed in claim 44, wherein said at least one data processor programmed to monitor loading is programmed to initiate the change of the assignment to the second data processor in response to a high loading condition on the first data processor.

46. The network file server as claimed in claim 44, wherein said at least one data processor programmed to monitor loading is programmed to initiate the change of the assignment to the second data processor in response to loading on the first data processor being relatively high and loading on the second data processor being relatively low.

47. The network file server as claimed in claim 43, wherein each data processor is programmed to forward the request over the network for continued processing by the data processor indicated by the stored assignment information as presently assigned to access the file system when said each data processor having received the request is different from the data processor indicated by the stored assignment information as presently assigned to access the file system.

48. The network file server as claimed in claim 47, wherein each data processor indicated by the stored assignment information as presently assigned to access the file system is programmed to return a response of each data access for a respective client over the network to a data processor having originally received a request for said each data access from the respective client, and the data processor having originally received said request for said each data access from the respective client is programmed to forward the response over the network to the respective client.

49. The network file server as claimed in claim 43, wherein each data processor has a file system cache of file data and file attributes for performing data access operations upon at least one file system to which said each data processor is assigned to access.

50. The network file server as claimed in claim 49, wherein each data processor is programmed for temporarily suspending processing for a request for access to said at least one file system to which said each data processor is assigned to access when there is a transfer of write-pending file data and file attributes for said at least one file system to which said each data processor is assigned to access from the file system cache of said each data processor to a file system cache of another one of the data processors for a change in the assignment of said each data processor to access said at least one file system to said another one of the data processors.

51. The network file server as claimed in claim 43, which further includes a cached disk storage subsystem for storing the read-write file systems, and wherein each of the data processors has a respective data link to the cached disk storage subsystem.

52. The network file server as claimed in claim 51, wherein the cached disk storage subsystem stores at least one read-only file system, and each of the data processors is programmed to receive from the network a client request for access to the read-only file system, and to respond to the client request for access to the read-only file system by accessing the read-only file system in the cached disk storage subsystem without any processing of the request for access to the read-only file system by another one of the data processors.

53. The network file server as claimed in claim 43, wherein the data processors are programmed so that the data processor indicated by the stored assignment information as presently assigned to access the file system accesses the file system for all client requests for access to files in the file system, including client requests received by a plurality of data processors in the network, unless and until there is a change in the stored assignment information.

54. The network file server as claimed in claim 43, wherein each data processor is programmed to check whether the data processor indicated by the stored assignment information as presently assigned to access the file system is different from said each data processor, and when the data processor indicated by the stored assignment information as presently assigned to access the file system is different from said each data processor, transmitting the request to the data processor indicated by the stored assignment information as presently assigned to access the file system, and when the data processor indicated by the stored assignment information as presently assigned to access the file system is not different from said each data processor, performing the data access operation upon the file system to which access is requested.

55. The network file server as claimed in claim 43, wherein each data processor indicated by the stored assignment information as presently assigned to access each file system is programmed to return a response for each access for a respective client to a data processor having originally received a request for said each access from said respective client, and the data processor having originally received the request for said each access from said respective client is programmed to forward the response over the network to said respective client.

56. The network file server as claimed in claim 43, wherein each data processor has disk storage for storing at least one file system to which said each data processor is assigned to access and for performing data access operations upon said at least one file system stored in the disk storage.

57. The network file server as claimed in claim 56, wherein each data processor is programmed for temporarily suspending processing for a request for access to said at least one file system to which said each data processor is assigned to access when there is a transfer of said at least one file system which said each data processor is assigned to access from the disk storage of said each data processor to disk storage of another one of the data processors for a change in the assignment of said each data processor to access said at least one file system to said another one of the data processors.

58. The network file server as claimed in claim 43, wherein each data processor has a cache of locking information and is programmed to manage read and write locks in the cache of locking information for access to at least one file system to which said each data processor is assigned to access.

59. The network file server as claimed in claim 43, wherein each data processor is programmed for temporarily suspending processing for a request for access to said at least one file system to which said each data processor is assigned to access when there is a transfer of locking information for said at least one file system to which said each data processor is assigned to access from said each data processor to another one of the data processors for a change in the assignment of said each data processor to access said at least one file system to said another one of the data processors.