Client server based multi-processor file system wherein client files written to by a client processor are invisible to the server

• US 5,758,342 A
• Filed: 01/23/1995
• Issued: 05/26/1998
• Est. Priority Date: 01/23/1995
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Gregerson, James Charles
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): ROBINSON, GRETA LEE
• Application Number:
  US08/376,710
• Time in Patent Office: 1,219 Days
• Field of Search: 395/600, 395/610, 395/200.01, 395/200.03, 395/608, 395/617, 395/200.33, 395/200.49, 707/10, 707/8, 707/201
• US Class Current: 707/758
• CPC Class Codes: G06F 16/10 File systems; File servers
• CPC Class Codes: Y10S 707/922 Communications
• CPC Class Codes: Y10S 707/99938 Concurrency, e.g. lock management in shared database
• CPC Class Codes: Y10S 707/99952 Coherency, e.g. same view to multiple users

Abstract

A distributed file system for a multi-processor system having multiple nodes, each node having a client processor and a client disk. The nodes are connected to a communications fabric for passing files between the nodes. One of the nodes acts as a server for passing files from the server to any of the other nodes. When a client processor reads a file on its client disk, the client processor obtains the server copy of the file and installs it on the client disk if the server copy of the file is more current, before the read operation. Provision is also made for atomically providing upgrades of application files to the client disks. When the client processor writes to a file, it sets a write flag in the file so that the file thus written to by the client processor is invisible to file operations from the server and the other nodes. The disclosed file system is particularly useful for systems administration of a multi-processor system having a single point of systems software install.

Claims

1. A file system comprising:

a plurality of nodes, each node having a client processor and a client disk for holding client files;

one of said nodes being a control node acting as a file server, the client disk of said control node being a server disk having server files corresponding to the client files;

communications fabric connected to said plurality of nodes for passing server files to said client disks; and

read/write means at each node for gaining access to specific files such that the client processor at each node may read from and write to files on the client disk at that node, said read/write means having;

determining means for determining if a specific file is on that client disk,

file import means for, in the event said determining means determines said specific file is not on the client disk, importing the corresponding server copy of the specific file over the communications fabric from the server disk to the client disk,

write testing means for testing if said specific file determined to be on the client disk as determined by said determining means has been written to by said client processor, and preventing said file import means from importing said specific file in the event said specific file has been written to, and

flagging means for flagging the client copy of the specific file with a write flag in the event that the client copy of the specific file is written to by the client processor.

2. The file system of claim 1 further comprising:

comparing means in each of said read/write means for, in the event said determining means determines said specific file is on the client disk and said write test means determines that the specific file has not been written to by the client processor, comparing whether the corresponding copy of the specific file on the server disk is more current than the specific file on the client disk and causing the file import means to import the corresponding server copy of the specific file over the communications fabric from the server disk to the client disk in the event the server file copy of the specific file is more current.

3. The file system of claim 2 wherein each file on said client disks and said server disk has a time stamp, and said comparing means compares the time stamp of said specific file on said client disk with the corresponding file on said server disk to determine if the corresponding file on said server disk is more current.

4. The file system of claim 2 wherein each file on said client disks has an install bit, said server has a server file command means for changing to an active status, the install bit of each file on the client disks whose corresponding file in the server disk has been changed to a more current version, and said comparing means compares the state of the install bit of said specific file such that if in an active state, said corresponding file on said server disk is more current.

5. The file system of claim 2 further comprising file command means at each node for performing file commands on files at the other nodes, and skip means in each read/write means for skipping client files on said client disks having a write flag during such file commands from other nodes, thereby making client files invisible to the file command means of other nodes.

6. The file system of claim 1 wherein said read/write means includes file creating means for creating a file to be written to on the client disk when the file to be written to does not exist on the client disk or the server disk.

7. The file system of claim 6 wherein said read/write means includes file deleting means to delete a file to make room on the client disk for a file being created by said file creating means.

8. The file system of claim 7 wherein said file deleting means includes aging logic for determining an aged out file to be deleted by said file creating means.

9. The file system of claim 8 wherein said aging logic uses least recently used logic.

10. The file system of claim 7 wherein said read/write means includes pinning means for pinning a file to said client disk such that said file deleting means will not delete a pinned file when making room for a file to be created by said file creating means.

11. The file system of claim 4 wherein said server disk includes:

one or more applications, each application having one or more files, at least one application having a lower version and a higher version;

trigger means for each application, said trigger means having a first state if the files to be imported for a specific application is to be from the lower version of the specific application and a second state if the files to be imported for said specific application is to be from the higher version of the specific application; and

each import means includes trigger comparison means for comparing the state of the trigger means for a file being imported from said server for determining if the file is to be imported from the lower level application or the higher level application.

12. The file system of claim 1 wherein said files include one or more pages, and said file import means includes means for importing said server copy of the specific file from the server disk to the client disk one page at a time.

13. In file system including a plurality of nodes, each node having a client processor and a client disk for holding client files, one of said nodes being a control node acting as a file server, the client disk of said control node being a server disk having server files corresponding to the client files, communications fabric connected to said plurality of nodes for passing server files to said client disks, and read/write means at each node for gaining access to specific files such that the client processor at each node may read from and write to files on the client disk at that node, a method comprising the steps of:

determining if a specific file is on that client disk,

in the event it is determined said specific file is not on the client disk, importing the corresponding server copy of the specific file over the communications fabric from the server disk to the client disk,

testing if said specific file determined to be on the client disk has been written to by said client processor,

preventing the importing of said specific file in the event said specific file has been written to, and

flagging the client copy of the specific file with a write flag in the event that the client copy of the specific file is written to by the client processor.

14. The method of claim 13 further comprising:

in the event it is determined that said specific file is on the client disk and the specific file has not been written to by the client processor, comparing whether the corresponding copy of the specific file on the server disk is more current than the specific file on the client disk; and

importing the corresponding server copy of the specific file over the communications fabric from the server disk to the client disk in the event the server file copy of the specific file is more current.

15. The method of claim 14 wherein each file on said client disks and said server disk has a time stamp, said method further comprising comparing the time stamp of said specific file on said client disk with the corresponding file on said server disk when determining if the corresponding file on said server disk is more current.

16. The file system of claim 14 wherein each file on said client disks has an install bit, said method further comprising changing to an active status, the install bit of each file on the client disks whose corresponding file on the server disk has been changed to a more current version, and comparing the state of the install bit of said specific file to see if it is in an active state when determining if said corresponding file on said server disk is more current.

17. The method of claim 14 further comprising performing client file operations by processors of any node on the other nodes in the file system, and making invisible to the other nodes, the client files on each client disk having a write flag which indicates the client file has been written to.

18. The method of claim 13 further comprising creating a file to be written to on the client disk when the file to be written to does not exist on the client disk or the server disk.

19. The method of claim 18 further comprising deleting a file to make room on the client disk prior to creating said file to be written to.

20. The method of claim 19 wherein file deleting step includes determining an aged out file to be deleted.

21. The method of claim 20 wherein said determining an aged out file uses least recently used logic.

22. The method of claim 19 further comprises pinning a file to said client disk such that said file deleting step will not delete a pinned file when making room for a file to be created by said file creating step.

23. The file system of claim 16 wherein said server disk includes:

one or more applications, each application having one or more files, at least one application having a lower version and a higher version;

trigger means for each application, said trigger means having a first state if the files to be imported for a specific application is to be from the lower version of the specific application and a second state if the files to be imported for said specific application is to be from the higher version of the specific application;

said method further comprising comparing the state of the trigger means for a file being imported from said server for determining if the file is to be imported from the lower level application or the higher level application.

24. A file system comprising:

a plurality of nodes, each node having a client processor and a client disk for holding client files;

one of said nodes being a control node acting as a file server, the client disk of said control node being a server disk having server files corresponding to the client files;

communications fabric connected to said plurality of nodes for passing server files to said client disks; and

means at each node for making files on the client disk that have been written to by the client processor at that node invisible to said file server and the other client nodes.

25. A file system comprising:

a plurality of nodes, each node having a client processor and a client disk for holding client files;

one of said nodes being a control node acting as a file server, the client disk of said control node being a server disk having operating system files;

communications fabric connected to said plurality of nodes for passing operating system files to said client disks;

file importing means at each node for importing specific operating system files from said server disk to the client disk at that node only when that client disk needs a specific operating system file; and

deleting means in said file importing means for deleting files from the client disk when there is not enough room to import a file from said server.

26. The filing system of claim 25 wherein said file importing means includes pinning means for pinning specific operating system files to said client disk such that the pinned files will not be deleted by said deleting means.