Network file server maintaining local caches of file directory information in data mover computers

• US 5,944,789 A
• Filed: 11/13/1996
• Issued: 08/31/1999
• Est. Priority Date: 08/14/1996
• Status: Expired due to Term

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Tzelnic, Percy, Vahalia, Uresh K
• Primary Examiner(s): Dinh, Dung C.
• Assistant Examiner(s): Le, Hieu C.
• Application Number:
  US08/748,363
• Time in Patent Office: 1,021 Days
• Field of Search: 395/200.08, 395/200.09, 395/200.66, 395/200.44, 395/726, 395/730, 395/650, 395/425, 395/800, 707/7, 707/8, 709/214, 711/145, 711/118
• US Class Current: 709/214
• CPC Class Codes: G06F 12/0813 with a network or matrix configuration
• CPC Class Codes: G06F 12/0815 Cache consistency protocols
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache
• CPC Class Codes: G06F 16/1774 Locking methods, e.g. locking methods for file systems allowing shared and concurrent access to files
• CPC Class Codes: G06F 2212/312 In storage controller
• CPC Class Codes: H04L 67/1095 Replication or mirroring of data, e.g. scheduling or transport for data synchronisation between network nodes
• CPC Class Codes: Y10S 707/99937 Sorting
• CPC Class Codes: Y10S 707/99938 Concurrency, e.g. lock management in shared database

Abstract

A network file server includes an integrated cached disk array and a plurality of data mover computers linking the cached disk array to the data network for file access. Each data mover computer maintains a local cache of file directory information including locking information of locked files that are accessible through the data mover. A cache consistency scheme ensures that shared locking information is consistent in the local caches. In a preferred embodiment, the cache consistency scheme uses an internal data link to pass messages between the data movers. The file directory information in the local cache includes information mapping file names to a list of logical blocks for each file name, file attributes that affect data access, and locking information down to a block level of granularity. Each data mover computer has network file manager software that maintains client ownership of locked files and communicates with the clients, and data mover file manager software that manages data mover computer ownership of locked files and communicates with other data mover computers. The cache consistency messages indicate a grant of data mover ownership over a file, a release of data mover ownership over a file, a denial of a request for access to a locked file, and changes to file attributes affecting access to a file. The local caches and the cache consistency scheme eliminate any need to store file locking information in the cached disk array.

Claims

1. A file server for serving clients in a data network, said file server comprising:

a cached disk storage subsystem including an array of disk drives and a semiconductor cache memory coupled to the disk drives for storage of data written to and read from the disk drives; and

a plurality of data mover computers linking the cached disk storage subsystem to the data network for responding to a request for file access from a client in the data network by transferring data between the cached disk storage subsystem and the data network, wherein the cached disk storage subsystem stores read-write files which are shared among the clients and are each accessible by the clients through more than one of the data mover computers, and wherein the file server maintains a file directory accessible by the data mover computers in response to file access requests to determine whether or not file access for a client is permitted, to map file names to logical blocks of data that comprise the files and are stored in the cached disk storage subsystem, and to lock and unlock each of the read-write files for shared read-write access among the clients through more than one of the data mover computers, and

wherein each data mover computer maintains a local cache of file directory information for locked files accessible by said each data mover computer, and wherein each data mover is computer programmed to respond to each request from a client serviced by said each data mover for access to a specified file by accessing the file directory to determine whether or not access to the specified file by said each client serviced by said each data mover computer is precluded by file access attributes of the specified file, and accessing the local cache of file directory information for locked files accessible by said each data mover computer to determine whether or not access to the specified file by said each client serviced by said each data mover computer is precluded by a lock on the specified file.

2. The file server as claimed in claim 1, wherein the local cache maintained by said each data mover computer includes an index of all locked files accessible by said each data mover computer.

3. The file server as claimed in claim 1, wherein the local cache maintained by said each data mover computer includes all file information affecting file access for all locked files accessible through said each data mover computer.

4. The file server as claimed in claim 3, wherein the local cache in said each data mover computer also includes a partial directory of file information for unlocked files.

5. The file server as claimed in claim 1, wherein said each data mover computer maintains a list of all locked portions of files accessible through said each data mover computer.

6. The file server as claimed in claim 1, wherein the file directory information in the local cache in said each data mover computer includes mapping information mapping file names to a list of logical blocks for each file name, file attributes that affect data access to each named file, and locking information down to a logical block level of granularity for each named file.

7. A file server for serving clients in a data network, said file server comprising:

a cached disk storage subsystem including an array of disk drives and a semiconductor cache memory coupled to the disk drives for storage of data written to and read from the disk drives; and

a plurality of data mover computers linking the cached disk storage subsystem to the data network for responding to a request for file access from a client in the data network by transferring data between the cached disk storage subsystem and the data network, wherein the cached disk storage subsystem stores read-write files which are shared among the clients and are each accessible by the clients through more than one of the data mover computers, and wherein the file server maintains a file directory accessible by the data mover computers in response to file access requests to determine whether or not file access for a client is permitted, to map file names to logical blocks of data that comprise the files and are stored in the cached disk storage subsystem, and to lock and unlock each of the read-write files for shared read-write access among the clients through more than one of the data mover computers, and

wherein each data mover computer maintains a local cache of file directory information for locked files accessible by said each data mover computer, and wherein each data mover computer is programmed to respond to each request from a client serviced by said each data mover for access to a specified file by accessing the file directory to determine whether or not access to the specified file by said each client serviced by said each data mover computer is precluded by file access attributes of the specified file, and accessing the local cache of file directory information for locked files accessible by said each data mover computer to determine whether or not access to the specified file by said each client serviced by said each data mover computer is precluded by a lock on the specified file; and

wherein the data mover computers are programmed to follow a cache consistency scheme to ensure that shared locking information is consistent in the local caches of the data mover computers.

8. The file server as claimed in claim 7, wherein the local cache maintained by said each data mover computer includes an index of all locked files accessible by said each data mover computer.

9. The file server as claimed in claim 7, wherein the local cache maintained by said each data mover computer includes all file information affecting file access for all locked files accessible through said each data mover computer.

10. The file server as claimed in claim 9, wherein the local cache in said each data mover computer also includes a partial directory of file information for unlocked files.

11. The file server as claimed in claim 7, wherein each data mover computer maintains a list of all locked portions of files accessible through said each data mover computer.

12. The file server as claimed in claim 7, wherein the file directory information in the local cache in said each data mover computer includes mapping information mapping file names to a list of logical blocks for each file name, file attributes that affect data access to each named file, and locking information down to a logical block level of granularity for each named file.

13. The file server as claimed in claim 12, wherein locking information for the files is not stored in the cached disk storage subsystem.

14. A file server for serving clients in a data network, said file server comprising:

a cached disk storage subsystem including an array of disk drives and a semiconductor cache memory coupled to the disk drives for storage of data written to and read from the disk drives;

a plurality of data mover computers linking the cached disk storage subsystem to the data network for responding to a request for file access from a client in the data network by transferring data between the cached disk storage subsystem and the data network; and

at least one data link internal to the file server and interconnecting the data mover computers for passing messages among the data mover computers;

wherein the cached disk storage subsystem stores read-write files which are shared among the clients and are each accessible by the clients through more than one of the data mover computers, and wherein the file server maintains a file directory accessible by the data mover computers in response to file access requests to determine whether or not file access for a client is permitted, to map file names to logical blocks of data that comprise the files and are stored in the cached disk storage subsystem, and to lock and unlock each of the read-write files for shared read-write access among the clients through more than one of the data mover computers, and

wherein each data mover computer maintains a local cache of file directory information for locked files accessible by said each data mover computer, and wherein each data mover computer is programmed to respond to each request from a client serviced by said each data mover for access to a specified file by accessing the file directory to determine whether or not access to the specified file by said each client serviced by said each data mover computer is precluded by file access attributes of the specified file, and accessing the local cache of file directory information for locked files accessible by said each data mover computer to determine whether or not access to the specified file by said each client serviced by said each data mover computer is precluded by a lock on the specified file; and

wherein the data mover computers are programmed to follow a cache consistency scheme to ensure that shared locking information is consistent in the local caches of the data mover computers, the cache consistency scheme passing messages over the data link among the data mover computers.

15. The file server as claimed in claim 14, wherein the local cache maintained by said each data mover computer includes an index of all locked files accessible by said each data mover computer.

16. The file server as claimed in claim 14, wherein the local cache maintained by said each data mover computer includes all file information affecting file access for all locked files accessible through said each data mover computer.

17. The file server as claimed in claim 16, wherein the local cache in each data mover computer also includes a partial directory of file information for unlocked files.

18. The file server as claimed in claim 14, wherein each data mover computer maintains a list of all locked portions of files accessible through said each data mover computer.

19. The file server as claimed in claim 14, wherein the file directory information in the local cache in said each data mover computer includes mapping information mapping file names to a list of logical blocks for each file name, file attributes that affect data access to each named file, and locking information down to a logical block level of granularity for each named file.

20. The file server as claimed in claim 19, wherein locking information for the files is not stored in the cached disk storage subsystem.

21. The file server as claimed in claim 14, wherein the messages include messages indicating grants of locks, and messages indicating releases of locks.

22. The file server as claimed in claim 21, wherein the messages further include messages indicating denials of locks.

23. The file server as claimed in claim 21, wherein the messages further include messages indicating changes to file attributes affecting file access.

24. The file server as claimed in claim 21, wherein the messages identify data mover ownership of locked files but do not identify client ownership of locked files.

25. The file server as claimed in claim 21, wherein the data mover computers are each programmed with a network file manager program for managing client ownership of files, and with a data mover file manager program for managing data mover computer ownership of files, and wherein the network file manager program manages communication with clients requesting file access, and the data mover file manager program manages communication of the messages among the data mover computers.

26. A file server for serving clients in a data network, said file server comprising:

a cached disk storage subsystem including an array of disk drives and a semiconductor cache memory coupled to the disk drives for storage of data written to and read from the disk drives;

a plurality of data mover computers linking the cached disk storage subsystem to the data network for responding to a request for file access from a client in the data network by transferring data between the cached disk storage subsystem and the data network; and

at least one data link internal to the file server and interconnecting the data mover computers for passing messages among the data mover computers;

wherein the cached disk storage subsystem stores read-write files which are shared among the clients and are each accessible by the clients through more than one of the data mover computers, and wherein the file server maintains a file directory accessible by the data mover computers in response to file access requests to determine whether or not file access for a client is permitted, to map file names to logical blocks of data that comprise the files and are stored in the cached disk storage subsystem, and to lock and unlock each of the read-write files for shared read-write access among the clients through more than one of the data mover computers, and

wherein each data mover computer maintains a local cache of file directory information for locked files accessible by said each data mover computer, and wherein each data mover computer is programmed to respond to each request from a client serviced by said each data mover for access to a specified file by accessing the file directory information to determine whether or not access to the specified file by said each client serviced by said each data mover computer is precluded by file access attributes of the specified file, and accessing the local cache of file directory information for locked files accessible by said each data mover computer to determine whether or not access to the specified file by said each client serviced by said each data mover computer is precluded by a lock on the specified file;

wherein the data mover computers are programmed to follow a cache consistency scheme to ensure that shared locking information is consistent in the local caches of the data mover computers, the cache consistency scheme passing messages over the data link among the data mover computers;

wherein the file directory information in the local cache in said each data mover computer includes, for each locked file accessible through said each data mover computer, mapping information mapping file names to a list of logical blocks for each file name, file attributes that affect data access to each named file, and all locking information down to a logical block level of granularity for each named file; and

wherein the messages include messages indicating grants of locks, messages indicating releases of locks, and messages indicating changes to file attributes affecting file access, and the messages indicating grants of locks identify data mover computer ownership of locked files but do not identify client ownership of locked files.

27. The file server as claimed in claim 26, wherein locking information for the files is not stored in the cached disk storage subsystem.

28. The file server as claimed in claim 26, wherein the messages further include messages indicating denials of locks.

29. The file server as claimed in claim 26, wherein the data mover computers are each programmed with a network file manager program for managing client ownership of files, and a data mover file manager for managing data mover computer ownership of files, and wherein the network file manager program manages communication with clients requesting file access, and the data mover file manager program manages communication of the messages among the data mover computers.

30. A method of operating a file server for serving clients in a data network, the file server including a cached disk storage subsystem and a plurality of data mover computers linking the cached disk storage subsystem to the data network for transfer of data between the cached disk storage subsystem and the data network, and the cached disk storage subsystem having an array of disk drives and a semiconductor cache memory for storing data written to and read from the array of disk drives, said method comprising the steps of:

(a) maintaining in each of the data mover computers a file directory of locked files accessible by the data mover computers in response to file access requests by the clients to determine whether or not file access by a client is permitted;

the locked files including read-write files which are shared among the clients, wherein the read-write files are accessible by the clients through more than one of the data mover computers;

the file directory in each of the data mover computers including file access information indicating whether or not file access is precluded by file access attributes of the files, and locking information indicating whether or not file access is precluded by locks on the files;

(b) one of the data mover computers receiving from one of the clients a request for file access to a specified file, said one of the data mover computers accessing the file directory to determine whether or not access to the specified file by said one of the clients is precluded by file access attributes of the specified file, and when access to the specified file by said one of the clients is not precluded by file access attributes of the specified file, accessing the file directory to determine whether or not access to the specified file by said one of the clients is precluded by a lock on the specified file, and when access to the specified file by said one of the clients is not precluded by a lock on the specified file, satisfying the request by transferring data between the cached disk storage subsystem and the data network.

31. The method as claimed in claim 30, wherein each data mover computer maintains in its local cache all file information affecting file access for all locked files accessible through said each data mover computer.

32. The method as claimed in claim 31, wherein each data mover computer retains in its local cache file information for unlocked files accessed through said each data mover computer until said each data mover computer needs memory for storing other information.

33. The method as claimed in claim 31, wherein each data mover computer maintains in its local cache, for each locked file accessible through said each data mover computer, mapping information mapping file names to a list of logical blocks for each file name, file attributes that affect data access to each named file, and locking information down to a logical block level of granularity for each named file.

34. A method of operating a file server for serving clients in a data network, the file server including a cached disk storage subsystem and a plurality of data mover computers linking the cached disk storage subsystem to the data network for transfer of data between the cached disk storage subsystem and the data network, and the cached disk storage subsystem having an array of disk drives and a semiconductor cache memory for storing data written to and read from the array of disk drives, said method comprising the steps of:

(a) maintaining in each of the data mover computers a file directory of locked files accessible by the data mover computers in response to file access requests by the clients to determine whether or not file access by a client is permitted;

the locked files including read-write files which are shared among the clients, wherein the read-write files are accessible by the clients through more than one of the data mover computers;

the file directory in each of the data mover computers including file access information indicating whether or not file access is precluded by file access attributes of the files, and locking information indicating whether or not file access is precluded by locks on the files;

(b) one of the data mover computers receiving from one of the clients a request for file access to a specified file, said one of the data mover computers accessing the file directory to determine whether or not access to the specified file by said one of the clients is precluded by file access attributes of the specified file, and when access to the specified file by said one of the clients is not precluded by file access attributes of the specified file, accessing the file directory to determine whether or not access to the specified file by said one of the clients is precluded by a lock on the specified file, and when access to the specified file by said one of the clients is not precluded by a lock on the specified file, satisfying the request by transferring data between the cached disk storage subsystem and the data network;

wherein the data mover computers employ a cache consistency scheme to ensure that shared locking information is consistent in the local caches of the data mover computers.

35. The method as claimed in claim 34, wherein each data mover computer maintains in its local cache all file information affecting file access for all locked files accessible through said each data mover computer.

36. The method as claimed in claim 34, wherein each data mover computer retains in its local cache file information for unlocked files accessed through said each data mover computer until said each data mover computer needs memory for storing other information.

37. The method as claimed in claim 34, wherein each data mover computer maintains in its local cache, for each locked file accessible through said each data mover computer, mapping information mapping file names to a list of logical blocks for each file name, file attributes that affect data access to each named file, and locking information down to a logical block level of granularity for each named file.

38. The method as claimed in claim 34, wherein the cached disk storage subsystem does not store any locking information for network files accessible through the data mover computers.

39. The method as claimed in claim 34, wherein the cache consistency scheme employs message passing among the data mover computers.

40. The method as claimed in claim 34, wherein the messages include messages indicating grants of locks, and messages indicating releases of locks.

41. The method as claimed in claim 39, wherein the messages further include messages indicating a denial of a request for access to a locked file.

42. The method as claimed in claim 41, wherein the messages indicating a denial of a request for access to a locked file are used to maintain a local wait list for each locked file when data mover computers are waiting for a lock to be released.

43. The method as claimed in claim 42, wherein a message indicating a denial of a request for access to a locked file is transmitted only when the data mover computer denying a client request would not already be a next data mover computer waiting for release of a lock on the locked file.

44. The method as claimed in claim 39, wherein the messages further include messages indicating changes to file attributes affecting file access.

45. The method as claimed in claim 39, wherein the messages identify data mover ownership of locked files but do not identify client ownership of locked files.