COORDINATED ACCESS TO A CLUSTERED FILE SYSTEM'S SHARED STORAGE USING SHARED-LOCK ARCHITECTURE

• US 20140095544A1
• Filed: 09/28/2012
• Published: 04/03/2014
• Est. Priority Date: 09/28/2012
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: ESHEL, Marc, HILDEBRAND, Dean, SCHMUCK, Frank B., WYLLIE, James C.
• Granted Patent: US 9,529,821 B2
• Time in Patent Office: Days
• US Class Current: 707/783
• CPC Class Codes: G06F 16/182 Distributed file systems

Abstract

Embodiments of the invention relate to coordinated access to a clustered file system'"'"'s shared storage subsystem using a shared-lock architecture. A particular file server is configured to coordinate the file system'"'"'s file access layout particular server, in response to a client'"'"'s file access layout request for byte-ranges of a file stored in the storage subsystem being received by a file server in cluster and sent to said particular server, generates a file access layout of a set of file servers for a parallel file access protocol to use and byte ranges of the file that particular individual file servers to use, to service an I/O request for the file. The file server (that received the request), sends the generated file access layout to said client, and requests coordinated access to said file from the particular server in response to receiving an I/O request to byte-ranges of said file.

Claims

1. A method of coordinated access to a clustered file system'"'"'s shared disk storage subsystem by using a shared-lock architecture, each active file server in the cluster having equivalent access to file system'"'"'s shared data, the method comprising:

receiving a file access layout request from a client for byte-ranges of a file stored in said subsystem;

generating a file access layout of a set of file servers for a parallel file access protocol to use and byte ranges of the file that particular individual file servers among said set to use, to service an I/O request for the file;

sending the generated file access layout to said client;

receiving from the client, an initial I/O request to byte-ranges of said file;

requesting coordinated access to said file from a file system byte-range coordinator that coordinates file system access to byte ranges of files stored in said subsystem;

validating that;

no file servers in said cluster have conflicting access to the file, byte ranges for the I/O requested are consistent with the generated file access layout, and said server (that received the I/O request) is the correct file server for byte ranges of the requested I/O based on the generated file access layout; and

if validated, then granting the server that received the initial I/O request coordinated access to the requested byte-ranges of the file.

2. The method of claim 1, wherein granting coordinated access thereby allows said server (that received the initial I/O request) to perform I/O to all byte-ranges of the file without further communication with file system.

3. The method of claim 1, wherein said server (that received the initial I/O request) retains the coordinated access until the byte range coordinator revokes said access.

4. The method of claim 1, further comprising:

when a file server in said cluster receives a I/O request from a client, subsequent to said initial request, for byte-ranges of the file, repeat said validating for the file server (that received said subsequent request).

5. The method of claim 4, further comprising:

if said server (that received said subsequent request) is validated for said subsequent request, then granting coordinated access to said server (that received said subsequent request) for the byte-ranges of the file in said subsequent request, and said server (that received said subsequent request) servicing said subsequent I/O request.

6. The method of claim 5, further comprising:

when coordinated access is granted to said server (that received said subsequent request), further subsequent I/O requests for said byte-ranges to the file are served by said server (that received said subsequent request) without further communication with the file system to coordinate the file system'"'"'s byte ranges.

7. The method of claim 4, further comprising:

if said server (that received said subsequent request) is not validated for said subsequent request, then;

(i) revokes coordinated access from all servers in the cluster for the file, (ii) said server (that received said subsequent request) requesting byte-range lock access for byte-ranges of the file associated with said subsequent request, (iii) if the file server is granted access to said byte range, the file server services the I/O request, and (iv) future I/O requests for byte-ranges to the file are coordinated by the file system until a coordinated access request for byte-ranges to the file is requested and granted to a file server.

8. The method of claim 1, further comprising:

if one or more other file servers in said cluster requests coordinated access to the same file as specified in said initial I/O request, repeating said validating; and

if validated and the server not already have coordinated access for the byte-range, granting the coordinated access to the one or more other file servers and the server that received the initial I/O request, in the order they are received from said servers.

9. The method of claim 1, further comprising:

if said server (that received said initial I/O request) is not validated, said server requests byte-range locks for access for each I/O to said file, the byte-range locks ensures updates and reads to said file from multiple servers in said cluster are synchronized.

10. The method of claim 9, wherein said byte range locks ensure POSIX semantics are maintained.

11. The method of claim 1, wherein coordinated access granted to a file server is retained until revoked by the file system or returned to by that file server.

12. The method of claim 1, wherein the file system ensures that the I/O performed by a file server to byte-ranges of a file is in a manner consistent with POSIX semantics.

13. A clustered file system of coordinated access to said file system'"'"'s shared disk storage subsystem by using a shared-lock architecture, said file system comprising:

a shared disk storage subsystem that stores said file system'"'"'s shared data;

a plurality of file servers, each of the file servers that are active having equivalent access to the shared data, wherein a particular file server (among said servers) is configured to coordinate the file system'"'"'s file access layout;

wherein said particular server, in response to a client'"'"'s file access layout request for byte-ranges of a file stored in said subsystem being received by a file server in cluster and sent to said particular server, generates a file access layout of a set of file servers for a parallel file access protocol to use and byte ranges of the file that particular individual file servers among said set to use, to service an I/O request for the file;

wherein said server (that received the file access layout request);

sends the generated file access layout to said client, and then requests coordinated access to said file from said particular server in response to receiving an I/O request to byte-ranges of said file; and

wherein said particular server validates that;

(i) no file servers in said cluster have conflicting access to said file, (ii) byte ranges for the I/O requested are consistent with the generated file access layout, and (iii) said server (that received the I/O request) is the correct file server for byte ranges of the requested I/O based on the generated file access layout, and if validated then the particular file server (configured to coordinate byte ranges) grants said server (that received the initial I/O request) coordinated access to the byte ranges of the file.

14. A computer program product of coordinated access to said file system'"'"'s shared disk storage subsystem by using a shared-lock architecture, wherein active file servers in said cluster have equivalent access to shared data of said file system, said program product comprising a computer readable storage medium having computer usable program code embodied therewith, said program code being readable/executable by a file system to:

receive a file system file access layout request from a client for byte-ranges of a file stored in said subsystem;

generate a file access layout of a set of file servers for a parallel file access protocol to use and byte ranges of the file that particular individual file servers among said set to use, to service an I/O request for the file;

send the generated file access layout to said client;

receive from the client, an initial I/O request to byte-ranges of said file;

request coordinated access to said file from a file system byte-range coordinator that coordinates file system access to byte ranges of files stored in said subsystem;

validate that;

no file servers in said cluster have conflicting access to the file, byte ranges for the I/O requested are consistent with the generated file access layout, and said server (that received the I/O request) is the correct file server for byte ranges of the requested I/O based on the generated file access layout; and

if validated, then granting the server, among said servers that received the initial I/O request, coordinated access to the byte-ranges of the file.

15. The computer program product of claim 14, said program code being further configured to:

when a file server in said cluster receives a I/O request from a client, subsequent to said initial request, for byte-ranges of the file, repeat said validate for the file server (that received said subsequent request).

16. The computer program product of claim 15, said program code being further configured to:

if said server (that received said subsequent request) is validated for said subsequent request, then grant coordinated access to said server (that received said subsequent request) for the byte-ranges of the file in said subsequent request, and said server (that received said subsequent request) services said subsequent I/O request.

17. The computer program product of claim 16, said being program code further configured to:

when coordinated access is granted to said server (that received said subsequent request), further subsequent I/O requests for said byte-ranges to the file are served by said server (that received said subsequent request) without further communication with the file system to coordinate the file system'"'"'s byte ranges.

18. The computer program product of claim 15, said program code being further configured to:

if said server (that received said subsequent request) is not validated for said subsequent request, then;

(i) revokes coordinated access from all servers in the cluster for the file, (ii) said server (that received said subsequent request) requests byte-range lock access for byte-ranges of the file associated with said subsequent request, (iii) if the file server is granted access to said byte range, the file server services the I/O request, and (iv) future I/O requests for byte-ranges to the file are coordinated by the file system until a coordinated access request for byte-ranges to the file is requested and granted to a file server.

19. The computer program product of claim 14, said program code being further configured to:

if one or more other file servers in said cluster requests coordinated access to the same as specified in said initial I/O request, repeats said validating; and

if validated, grants the coordinated access to said other servers and said server (that received the initial I/O request) in parallel.

20. The computer program product of claim 14, said program code being further configured to:

if said server (that received said initial I/O request) is not validated, said server requests byte-range locks for access for each I/O to said file, the byte-range locks ensures updates and reads to said file from multiple servers in said cluster are synchronized.