Term-based methods and apparatus for access to files on shared storage devices

• US 6,658,417 B1
• Filed: 10/13/2000
• Issued: 12/02/2003
• Est. Priority Date: 12/31/1997
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Haselton, William, Stakutis, Christopher J.
• Primary Examiner(s): Rones, Charles
• Assistant Examiner(s): Wu, Yicun
• Application Number:
  US09/687,390
• Time in Patent Office: 1,145 Days
• Field of Search: 707/100, 707/205, 707/204, 707/200, 707/10, 707/8, 707/202, 707/1, 707/201, 710/38, 710/20, 710/39, 711/1, 711/113, 711/162, 711/111, 711/171, 709/215, 709/240, 709/203, 709/217, 709/226, 709/223, 712/10, 705/43, 714/6, 700/5, 702/176, 341/106, 379/93.25, 345/835, 345/502, 235/380, 370/238, 370/401, 360/48, 365/230.03, 369/30.31
• US Class Current: 1/1
• CPC Class Codes: G06F 16/10 File systems; File servers
• CPC Class Codes: G06F 2003/0697 device management, e.g. handlers, drivers, I/O schedulers
• CPC Class Codes: G06F 3/0601 Interfaces specially adapted for storage systems
• CPC Class Codes: G06F 3/0604 Improving or facilitating administration, e.g. storage management
• CPC Class Codes: G06F 3/0622 in relation to access
• CPC Class Codes: G06F 3/0637 Permissions
• CPC Class Codes: G06F 3/0643 Management of files
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]
• CPC Class Codes: Y10S 707/99952 Coherency, e.g. same view to multiple users

Abstract

Methods and apparatus for accessing files on networked digital data processing system provide for plurality of digital data processing nodes and a storage device, e.g., a disk drive, a “jukebox,” other mass storage device or other mapped device (collectively referred to herein after as “disk drive” or “storage device”). First and second ones of the nodes, which may be a client and a server node, respectively, are coupled for communication over a first communications pathway, e.g., a LAN or other network. Both the first and the second nodes are in communication coupling with the storage device over the same or different logical or physical communications pathways. A file system or other functionality in the second (server) node receives and responds to at least selected requests—e.g., file OPEN requests—from the first (client) node for access to a file on the storage device, by generating a “lease”. The lease includes a block map or other administrative data (referred to elsewhere herein as “meta data”) for the requested file, as well as an expiry time indicating how long the administrative data is valid. Upon grant of the lease, the client node accesses the storage device using the block map or other administrative data supplied with the lease. The server node assures that this administrative data remains valid for the period of the lease, e.g., such that the client node may directly access the requested file without risk that another node (or the server itself) has changed it. Correspondingly, the client node ceases utilization of the administrative data (and, presumably, ceases at least direct access of the file) after lease expiry.

Claims

1. A digital data processing system with improved access to information stored on a storage device, said system comprising:

a first node and a second node coupled to one another over a network or other communications pathway, at least the second node being coupled to a storage device; and

a file system executing on at least the second node, the file system responding to a request by the first node by issuing a lease, the lease including a map pertaining to a file identified by the request and having a defined lease time; and

the first node utilizing the map in connection with accessing the file for the defined lease time, wherein the defined lease time has a lease expiry time referenced to a request time whereby the first and second node accurately determine the lease expiry time without requiring network time synchronization.

2. The digital data processing system of claim 1, wherein the file system determines change data for outstanding leases, and maintains meta data for files on the storage device.

3. The digital data processor of claim 1, wherein the file system sets a the lease time as a function of one or more of file size, number of outstanding leases, access request type, and network response time.

4. The digital data processor of claim 1, wherein the file system interfaces with a native file system meta data controller layer to unlock files and permit changes of block addresses after expiry of the lease.

5. The digital data processor of claim 1, wherein the file system interfaces with a native file system meta data controller layer to lock files or block addresses upon issuance of the lease.

6. The digital data processor of claim 1, further comprising a file application running on the first node configured to prevent the first node from accessing or referencing data of a requested file after expiry of the lease granted for said file.

7. The digital data processor of claim 1, wherein the file system sets the lease time as a function as a constant function of file access request type (read-only or read-write).

8. A digital data processing system with improved access to information stored on a storage device, said system comprising

a first node and a second node coupled to one another over a network or other communications pathway, at least the second node being coupled to a storage device, and;

a file system executing on at least the second node, the file system responding to a request by the first node by issuing a lease, the lease including administrative data pertaining to a file identified by the request and having a defined lease time;

the first node utilizing the map in connection with accessing the file for the defined lease time; and

a file application running on the first node configured to prevent the first node from accessing or referencing data of a requested file after expiry of the lease granted for said file, wherein the file application running on the first node operates to complete a file write and report end-of-file pointer to the second node prior to lease expiry.

9. A digital data processing system with improved access to information stored on a storage device, said system comprising;

a first node and a second node coupled to one another over a network or other communications pathway, at least the second node being coupled to a storage device,

a file system executing on at least the second node, the file system responding to request by the first node by issuing a lease, the lease including administrative data pertaining to a file identified by the request and having a defined lease time,

the first node utilizing the map in connection with accessing the file for the defined lease time,

wherein the file system executing on the second node includes an interface layer effective to transfer data designated by the request between the first node and the storage device via the second node, while maintaining administrative information pertaining to storage of the data designated by the request on the storage device, and to implement a bypass for interceding in response to at least a first selected access request applied thereby to the file system, by transferring data designated by that request between the first node and the storage device over a direct communications pathway in accord with administrative information maintained by the file system pertaining to storage of that data on the storage device while maintaining file coherence and security.

10. A method of permitting shared access to storage for files in a networked system, wherein the networked system includes first nodes, such method comprising the steps of:

responding to a file request by a first node by providing a lease having a lease time, wherein the lease includes a map for accessing the file in a storage device;

permitting the first node to directly access the storage device during the lease time;

assuring that the map remains valid during the lease time by providing a file system operative on a second node, wherein the second node interfaces with the storage system by interfacing with a native file system meta data controller to lock the file when a the lease is provided to prevent re-allocation of block addresses of the file during the lease time, whereby the first node may directly access the file without extraneous messaging over the networked system to coordinate file access and maintain coherence.

11. A method of permitting shared access to storage for files in a networked system, wherein the networked system includes first nodes, such method comprising the steps of:

responding to a file request by a first node by providing a lease having a lease time, wherein the lease includes a map for accessing the file in a storage device;

permitting the first node to directly access the storage device during the lease time;

assuring that the map remains valid during the lease time by providing a file system operative on a second node, wherein the second node interfaces with the storage system by interfacing with a native file system meta data controller to unlock the file upon expiry of the lease time of an outstanding lease to prevent re-allocation of block addresses of the file during the lease time, whereby the first node may directly access the file without extraneous messaging over the networked system to coordinate file access and maintain coherence.

12. A method of permitting shared access to storage for files in a networked system, wherein the networked system includes first nodes, such method comprising the steps of:

responding to a file request by a first node by providing a lease having a lease time, wherein the lease time is set as a function of one or more of file size, number of outstanding leases, as a constant function of access request type (read-only, read-write), and network response time, wherein the lease includes a map for accessing the file in a storage device;

permitting the first node to directly access the storage device during the lease time; and

assuring that the map remains valid during the lease time whereby the first node may directly access the file without extraneous messaging over the networked system to coordinate file access and maintain coherence.

13. A method of permitting shared access to storage for files in a networked system, wherein the networked system includes first nodes, such method comprising the steps of:

responding to a file request by a first node by providing a lease having a lease time, wherein the lease includes a map for accessing the file in a storage device;

permitting the first node to directly access the storage device during the lease time; and

assuring that the map remains valid during the lease time whereby the first node may directly access the file without extraneous messaging over the networked system to coordinate file access and maintain coherence, wherein the lease time has a lease expiry time referenced to a file request time whereby the first and second node accurately determine the lease expiry time without requiring network time synchronization.

14. The method of claim 13, wherein the step of assuring that the map remains valid is effected by providing a file system operative on a second node, wherein the second node interfacing with the storage system to prevent re-allocation of block addresses of the file during the lease time.

15. The method of claim 13, wherein the step of permitting is effected by providing a file system on the first node effective to directly access the file during the lease time using the map.

16. The method of claim 15, wherein the file system on the first node is configured to prevent the first node from accessing or referencing data of a requested file after expiry of the lease granted for said file.

17. The method of claim 13, wherein the step of providing a lease includes setting a lease time referenced to time of a file request message.

18. The method of claim 13, wherein the step of providing a lease includes setting a lease time as a function of one or more of file size, number of outstanding leases, access request type (read-only, read-write), and network response time.

19. The method of claim 13, further comprising the step of preventing the first node from accessing or referencing data of a requested file after expiry of a lease granted for said file.