Distributed storage management system having a cache server and method therefor

• US 5,940,594 A
• Filed: 07/29/1997
• Issued: 08/17/1999
• Est. Priority Date: 05/31/1996
• Status: Expired due to Term

• Current Assignee: HGST Netherlands B.V. (Western Digital Corporation)
• Original Assignee: International Business Machines Corporation
• Inventors: Lee, Thomas S., Kozina, Gerald Edward, Hu, Tawei, Ali, Seifu, Burket, Thomas G.
• Primary Examiner(s): Ramirez, Ellis B.
• Assistant Examiner(s): Austin-Hollands, Christian
• Application Number:
  US08/902,285
• Time in Patent Office: 749 Days
• Field of Search: 364/284.4, 364/280, 364/242.94, 364/284, 395/200.59, 395/680, 395/683, 395/200.33, 707/8
• US Class Current: 709/203
• CPC Class Codes: G06F 16/10 File systems; File servers

Abstract

The present invention is directed to a method and system for storing and managing objects, such as binary large objects (blobs) in a digital library system which includes a plurality of clients, an object server for storing an object, a cache server for storing an copy of the object, and a centralized server for storing information identifying the object as being stored in the object server and associating one or more of the clients with the cache server, in which one of the clients, as a requesting client, requests retrieval of an object, a copy of the requested object is sent from the cache server to the requesting client if the object is stored in said cache server, and a copy of said object is sent from the object server to said requesting client if the object is not stored in the cache server; and a copy of the requested object is sent from the object server to the cache server after the object server sends the object to the client, in which the object sent to the client is made available to the client regardless of whether sending of the copy of the object to the cache server is completed.

Claims

1. A computer-implemented process for storing and managing objects in a distributed information storage management system including a plurality of clients, an object server for storing an object, a cache server and a centralized server having information stored therein regarding the location of the object, the plurality of clients and the cache server, and identifying an association between two or more of the plurality of clients and the cache server, the computer-implemented process comprising the steps of:

a) the centralized server receiving a request from one of the plurality of clients as a requesting client for retrieval of the object, and in response thereto sending a request for the object to the cache server associated with the requesting client;

b) sending a copy of the object requested in step a) from the cache server to said requesting client if the object is present in said cache server;

c) sending a copy of the object requested in step a) from the object server to said requesting client if the object is not present in the cache server; and

d) sending another copy of the object requested in step a) from the object server to the cache server after step c) begins, wherein steps b), c) and d) are initiated by the centralized server based on the information stored in said centralized server.

2. The computer-implemented process recited in claim 1, wherein the information stored in the centralized server identifies the object as being stored in said object server.

3. The computer-implemented process recited in claim 1, wherein the centralized server causes said copy of the object sent to said client to become available for use to said client regardless of whether step d) is completed.

4. The computer-implemented process recited in claim 1, wherein said requesting client includes a client cache which is a persistent data store, and said copy of the object sent to said requesting client in one of steps b) and c) is stored in said client cache.

5. The computer-implemented process recited in claim 1, wherein said requesting client includes a client cache which is a non-persistent data store, and said copy of the object sent to said requesting client in one of steps b) and c) is stored in said client cache.

6. A computer-implemented process for storing and managing objects in a distributed information storage management system including a plurality of clients, an object server for storing an object, a cache server and a centralized server for storing information regarding the location of the object, the object server, the cache server and the plurality of clients, the computer-implemented process comprising the steps of:

a) the centralized server receiving a request from a first one of the plurality of clients as a first requesting client for storing a copy of the object in the cache server, and in response thereto sending a request for the object to the object server;

b) sending a copy of the object requested in step a) from said object server to said cache server and storing said copy of the object in the cache server;

c) the centralized server receiving a request from a second one of the plurality of clients as a second requesting client for retrieving a copy of the object, and in response thereto sending a request for the object to the cache server; and

d) sending said copy of the object requested in step c) from the cache server to said second requesting client in response to the request to the cache server in step c).

7. The computer-implemented process recited in claim 6, wherein the information stored in the centralized server identifies the object as being stored in the object server and identifies an association between one or more of the plurality of clients and the cache server.

8. The computer-implemented process recited in claim 6, wherein said second requesting client is any one of the plurality of clients associated with the cache server as identified by the information stored in the centralized server.

9. A computer-readable medium of instructions for causing a computer to store and manage objects in a distributed information storage management system including a plurality of clients, an object server for storing an object, a cache server and a centralized server having information stored therein regarding the location of the object, the plurality of clients and the cache server, and identifying an association between two or more of the plurality of clients and the cache server, the computer-readable medium of instructions comprising:

means for the centralized server receiving a request from one of the plurality of clients as a requesting client to retrieve the object, and in response thereto sending a request for the object to the cache server if the cache server is associated with the requesting client;

means for sending a copy of the object requested from the cache server to said requesting client if the object is present in said cache server;

means for sending a request for the object from the centralized server to the object server, if the object is not present in said cache server,

means for sending a copy of the object requested from the object server to said requesting client if the object is not present in the cache server; and

means for sending another copy of the object requested from the object server to the cache server after said means for sending the copy of the object requested from the object server begins sending the object, wherein said means for sending a copy of the object requested from the cache server, said means for sending a copy of the object requested from the object server and said means for sending another copy of the object begin operating in response to the centralized server based on the information stored in said centralized server.

10. The computer-readable medium of instructions recited in claim 9, wherein the information stored in the centralized server identifies the object as being stored in said object server.

11. The computer-readable medium of instructions recited in claim 9, wherein the centralized server causes said copy of the object sent to said client to become available for use to said client regardless of whether said means for sending another copy of the object completes sending the other object.

12. The computer-readable medium of instructions recited in claim 9, wherein said requesting client includes a client cache which is a persistent data store, and said copy of the object sent to said requesting client by one of said means for sending a copy of the object requested from the cache server and said means for sending a copy of the object requested from the object server is stored in said client cache.

13. The computer-readable medium of instructions recited in claim 9, wherein said requesting client includes a client cache which is a non-persistent data store, and said copy of the object sent to said requesting client by one of said means for sending a copy of the object requested from the cache server and said means for sending a copy of the object requested from the object server is stored in said client cache.

14. A computer-readable medium of instructions for causing a computer to store and manage objects in a distributed information storage management system including a plurality of clients, an object server for storing an object, a cache server and a centralized server for storing information regarding the location of the object, the object server, the cache server and the plurality of clients, the computer-readable medium of instructions comprising:

means for storing a copy of the object in the cache server in response to the centralized server receiving a request from a first one of the plurality of clients as a first requesting client to store the object in the cache server, and in response thereto sending a request for the object to the object server;

means for sending a copy of the object requested from said object server to said cache server and storing said copy of the object in the cache server;

means for the centralized server receiving a request from a second one of the plurality of clients as a second requesting client to retrieve a copy of the object, and in response thereto sending a request for the object to the cache server; and

means for sending said copy of the requested object from the cache server to said second requesting client in response to the request to the cache server.

15. The computer-readable medium of instructions recited in claim 14, wherein the information stored in the centralized server identifies the object as being stored in the object server and identifies an association between one or more of the plurality of clients and the cache server.

16. The computer-readable medium of instructions recited in claim 14, wherein said second requesting client is any one of the plurality of clients associated with the cache server as identified by the information stored in the centralized server.

17. A programmable apparatus directed by a computer program for storing and managing objects, comprised of:

a plurality of clients;

an object server for storing an object;

a cache server; and

a centralized server having information which identifies an association between two or more of said plurality of clients and said cache server,

wherein when said centralized server receives a request from one of said plurality of clients as a requesting client for retrieval of said object said centralized server based on the association information, directs said cache server to send a copy of said object to said requesting client if an instance of said object is stored in said cache server, otherwise said centralized server directs said object server to send an copy of said object to said requesting client.

18. The programmable apparatus recited in claim 17, wherein said centralized server stores information which identifies said object as being stored in said object server and wherein said centralized server directs said object server and said cache server based on said information stored in said centralized server.

19. The programmable apparatus recited in claim 18, wherein after one of said cache server and said object server begins to send said copy of said object to said requesting client said centralized server directs said object server to send another copy of said object to said cache server if an instance of said object is not stored in said cache server, wherein said centralized server causes said copy of said object sent to said requesting client to become available for use by said client regardless of whether said object server has completed sending the other copy of said object to said cache server.

20. A programmable apparatus directed by a computer program for storing and managing objects, comprised of:

a plurality of clients;

an object server for storing an object;

a cache server for storing an instance of said object; and

a centralized server for storing information identifying said object as being stored in said object server and associating two or more of said plurality of clients with said cache server,

wherein a first requesting client from among said plurality of clients sends a request for said object to said centralized server and in response to said request said centralized server sends a request to said cache server to send a copy of said instance of said object to said first requesting client if said first requesting client is a member of said two or more clients associated with said cache server, otherwise said centralized server sends a request to said object server to send a copy of said object to said first requesting client.

21. The programmable apparatus recited in claim 20, wherein in response to said request sent from said centralized server to said cache server, said cache server sends said copy of said instance of said object to said first requesting client if it is a member of said two or more clients associated with said cache server, otherwise in response to said request sent from said centralized server to said object server, said object server sends said copy of said object to said first requesting client, and said centralized server notifies said first requesting client once said copy of said object is sent by one of said cache server and said object server, and said object becomes available for use by said first requesting client.

22. The programmable apparatus recited in claim 20, wherein when another of said plurality of clients as a second requesting client sends a request to said centralized server for retrieval of another object which is stored in said object server but is not stored in said cache server, said centralized server sends a request to said object server to send a copy of said other object to said second requesting client, said centralized server sends a request to said cache server to retrieve a copy of said object from said object server, and said centralized server notifies said second requesting client once said copy of said other object is sent to said second requesting client, and upon receipt of said notice from said centralized server said copy of said object becomes available for use by said second requesting client, wherein said centralized server sends said notice regardless of whether said cache server retrieves a copy of said other object from said object server.

23. The programmable apparatus recited in claim 20, wherein another of said plurality of clients as a second requesting client sends a request to said centralized server to store in said cache server a copy of another object, and in response to said request from said second requesting client said centralized server sends a request to said cache server to retrieve a copy of the other object from said object server whereupon said object server sends a copy of said other object to said cache server.

24. The programmable apparatus recited in claim 23, wherein yet another of said plurality of clients as a third requesting client sends a request to said centralized server to retrieve a copy of the other object based upon a predetermined condition, whereupon said centralized server sends a request to said cache server which in response thereto sends said copy of said other object to said third requesting client.

25. The programmable apparatus recited in claim 24, wherein said first, second and third requesting clients are the same one of said plurality of clients.

26. The programmable apparatus recited in claim 21, wherein said first requesting client comprises:

a client cache for persistently storing said copy of said object received from one of said object server and said cache server; and

a client application program for retrieving said object from said client cache upon receipt of said notice from said centralized server.

27. The programmable apparatus recited in claim 21, wherein said first requesting client comprises:

a non-persistent storage area for storing said copy of said object received from one of said object server and said cache server, wherein upon receipt said copy of said object is stored only in said non-persistent storage area; and

a client application program for retrieving said copy of said object from said non-persistent storage area upon receipt of said notice from said centralized server.

28. The programmable apparatus recited in claim 20, wherein when said object server stores another object which is identified in said centralized server as being stored in said object server, said centralized server causes a copy of the other object to be stored in said cache server.