Methods and apparatus for providing access by a first computing system to data stored in a shared storage device managed by a second computing system

• US 6,718,372 B1
• Filed: 01/07/2000
• Issued: 04/06/2004
• Est. Priority Date: 01/07/2000
• Status: Expired due to Term

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Bober, Paul M.
• Primary Examiner(s): Dharia, Rupal
• Assistant Examiner(s): Pollack, Melvin H.
• Application Number:
  US09/479,512
• Time in Patent Office: 1,551 Days
• Field of Search: 709/211-219, 709/248-249, 709/325, 711/147-153
• US Class Current: 709/217
• CPC Class Codes: G06F 16/183 Provision of network file services by network file servers, e.g. by using NFS, CIFS network file access protocols H04L67/1097
• CPC Class Codes: G06F 16/188 Virtual file systems

Abstract

The system of the invention is a data server that can provide access to data, such as mainframe data, by open systems platforms. The system includes a shared storage interface coupling a first computing system to a shared storage device in which the shared data is maintained by a second computing system in a manner that is not natively compatible to the first computing system. The computing system further includes a data access server which executes on the processor in the first computing system. When executing, the data access server receives, via the network interface, a client message to access data on the shared storage device and in response to receiving the client message, retrieves, via the network interface, data storage information provided from the second computing system coupled to the first computing system. The data storage information is stored in the memory system and allows the data access server on the first computing system to access the data in the shared storage device in a manner that is compatible with the first computing system. The data access server can also provide a virtual file system to allow networked clients that implement file or other data sharing protocols such as NFS and CIFS.

Claims

1. A method for providing access by a first computing system to data stored in a shared storage device managed by a second computing system, wherein a data storage format provided in the shared storage by the second computing system is incompatible with a data storage format required by the first computing system, the method comprising the steps of:

receiving, at a data access server performed on a first computing system, a client message to access data on the shared storage device;

in response to receiving the client message, retrieving data storage information provided from the second computing system coupled to the first computing system, the data storage information allowing the first computing system to access the data in the shared storage device in a manner that is compatible with the first computing system, retrieving the data storage information further comprising;

first determining if suitable data storage information is available locally on the first computing system to allow the data access server to provide access to the data on the shared storage device in accordance with the client message in a manner that is compatible with the first computing system, and if so;

using the suitable data storage information that is available locally on the first computing system as the retrieved data storage information;

and if not;

retrieving, from the second computing system, the data storage information that is required for accessing the data in the shared storage device in a manner that is compatible with the first computing system; and

providing compatible access to the data on the shared storage device, directly from the data access server, based on the retrieved data storage information, the direct, compatible access alleviating processor resources of the second computing system from the compatible access.

2. The method of claim 1 wherein the data access server is a distributed data server and the step of receiving the client message includes the steps of:

providing, from the data access server to at least one data access client requiring access to data in the shared storage device, a distributed data interface that operates according to a distributed data protocol; and

accepting the client message from the at least one data access client using the distributed data protocol over the distributed data interface provided by the data access server, the client message including a data access command formatted in accordance with the distributed data protocol, the data access command indicating a type access to be provided to the data in the shared storage device on behalf of the client.

3. The method of claim 2 wherein:

the data access server is a distributed file system data access server and the distributed data interface is a distributed file system interface provided by the data access server and the distributed data protocol is a distributed file system protocol; and

wherein the step of accepting the client message includes the step of receiving the client message from the at least one data access client in accordance with the distributed file system protocol.

4. The method of claim 3 wherein the distributed file system protocol is at least one of a network file system protocol, a web based network file system protocol and a CIFS protocol.

5. The method of claim 2 wherein the distributed data protocol is at least one of a CORBA data exchange protocol, a Java beans based messaging protocol, and a hypertext transfer protocol.

6. The method of claim 2 wherein the at least one data access client requiring access to data in the shared storage device is performed on a computing system that is different than the first computing system and wherein the steps of providing and accepting are performed by the data access server using the distributed data access protocol over a network coupling the first computing system with the computing system performing the at least one data access client.

7. The method of claim 1 wherein the step of retrieving data storage information retrieves the data storage information from a virtual file system maintained in the first computing system by the data access server, the virtual file system obtaining the data storage information from the second computing system prior to receipt of the client message in response to processing formerly received client messages.

8. The method of claim 7 wherein the step of retrieving the data storage information from the virtual file system includes the steps of:

searching a number of unodes in the virtual file system to obtain a unode corresponding to the data to which access is requested in the client request message; and

obtaining the data storage information from the virtual file system based on the unode.

9. The method of claim 1 wherein the step of providing access to the data on the shared storage device based on the retrieved data storage information includes the step of:

performing, by the data access server, at least one data access routine to access the data in the shared storage device in a manner specified in the client message, the at least one data access routine using the data storage information to properly locate and access the data in a format that is compatible with the first computing system.

10. The method of claim 9 wherein:

the client message requests read access to the data in the shared storage on behalf of an application; and

the step of performing the at least one data access routine to access the data in the shared storage device includes the steps of;

reading the data in a manner specified in the client message from the shared storage device at a location specified by the retrieved data storage information; and

returning the data read by the step of reading from the data access server to a data access client that originated the client message.

11. The method of claim 1 wherein the first computing system is an open systems computing system and the second computing system is a mainframe computing system and the step of receiving a client message includes the step of:

allowing at least one data access client to access the data access server using a distributed file system protocol to request access via the data access server to mainframe data maintained by the mainframe computing system in the shared storage device;

and wherein the step of providing access to the data on the shared storage device from the data access server includes the steps of;

using the data storage information retrieved from the mainframe computing system to directly and compatibly access, by the data access server, the data stored on the shared storage device as specified by a command in the client message; and

serving the data to the at least one data access client from the data access server using the distributed file system protocol.

12. The method of claim 11 wherein:

the at least one data access client is performed on the first computing system and acts on behalf of an application also performed on the first computing system; and

wherein the steps of retrieving the client message and providing access to the data are performed between the data access client and the data access server using the distributed file system protocol within the first computing system.

13. The method of claim 11 wherein the at least one data access client is a plurality of data access clients and the step of serving the data includes the step of serving data maintained by the mainframe in the shared storage device from the data access server on the first computing system to the plurality of data access clients using a distributed file system protocol.

14. The method of claim 12 wherein at least one of the plurality of data access clients is performed on a computing system that is different that the first and second computing systems and the steps of retrieving the client message and providing access to the data are performed over a network coupling the first computing system and the computing system that is performing the data access client.

15. The method of claim 1 further including the step of:

maintaining, on the first computing system, a virtual file system containing a plurality of nodes, with at least one node for each portion of data for which access is requested via client messages; and

wherein the step of retrieving the data storage information includes the steps of;

determining if the data for which access is requested via the client message has a corresponding node in the virtual file system, and if so;

retrieving the data storage information from the corresponding node in the virtual file system;

and if not;

retrieving the data storage information from the second computing system;

creating at least one node in the virtual file system based on the retrieved data storage information; and

putting at least a portion of the data storage information retrieved from the second computing system into the node created for that data in the virtual file system.

16. The method of claim 15 wherein the step of maintaining includes the step of:

maintaining each of the plurality of nodes in the virtual file system on the first computing device in a hierarchical format, with different levels of the hierarchical format representing different elements of a storage system managed by the second computing system.

17. The method of claim 16 wherein the hierarchical format maps a mainframe storage arrangement of the data stored in the shared storage device to an open systems file system arrangement.

18. The method of claim 15 wherein the step of maintaining maintains, for each node in the virtual file system, information concerning the relation of that node to other nodes in the virtual file system and a unique handle for the node.

19. The method of claim 15 wherein the step of maintaining maintains, for each node in the virtual file system, data access information including at least one access position for the data within the shared storage device.

20. The method of claim 1 wherein the step of retrieving data storage information includes the steps of:

determining if appropriate data storage information is available in a virtual file system maintained by the data access server on the first computing system based on client request parameters in the client message,

and if not;

selecting at least one first data access routine based on a protocol command specified by the client message;

performing the at least one first data access routine to allow the data access server on first computing system to communicate with the second computing system to request the data storage information from the second computer system;

receiving a response to the at least one data access routine from the second computer system; and

parsing the response to the at least one data access routine to determine the data storage information and placing the data storage information into the virtual file system maintained by the data access server on the first computing system;

and if so;

translating client request parameters contained in the client message into data access parameters useable for the selected at least one data access routine, the step of translating using data storage information contained in a virtual file system to provide a location in the shared storage device of data for which access is specified in the client request message.

21. The method of claim 20 wherein the step of translating client request parameters contained in the client message includes the steps of:

obtaining at least one client request parameter from the client message; and

mapping the at least one client request parameter to at least one data access routine parameter required for performance of the at least one data access routine, the at least one data access routine parameter specifying data storage information to allow the data access routine to obtain access to a location of data within the shared storage device.

22. The method of claim 21 wherein the step of mapping includes the steps of:

using data access translator functions to query a virtual file system of unodes for a specific unode corresponding to a data access handle provided in the client message;

obtaining from the unode the data storage information.

23. The method of claim 20 wherein the step of performing the at least one data access routine includes the step of communicating between the data access server on the first computing system and a data access agent on the second computing system to obtain the data storage information required to perform the protocol command specified by the client message.

24. The method of claim 23 wherein:

the first computing device is an open system computing system and the second computing device is a mainframe and the data storage information is contained within metadata maintained within the mainframe; and

wherein the step of communicating sends a request to the data access agent to return metadata obtained from a mainframe catalog for the shared storage device, the metadata including storage information for the data maintained by the mainframe in the shared storage device.

25. The method of claim 1 wherein the step of providing access to the data on the shared storage device includes the steps of:

mapping the data storage information into at least one data access routine parameter of at least one data access routine;

directly accessing the shared storage device by performing the at least one data access routine to send data access requests to the shared storage device; and

retrieving, in response to the data access requests, a storage device response including data for which access is requested in the client message; and

providing the data to a data access client that originated the client message.