Transferring data in a digital data processing system

• US 5,247,618 A
• Filed: 05/11/1992
• Issued: 09/21/1993
• Est. Priority Date: 06/30/1989
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Digital Equipment Corporation (HP Inc.)
• Inventors: Bean, Robert G., Thiel, David W., Davis, Scott H., Goleman, William L., Zahrobsky, James A.
• Primary Examiner(s): Fleming, Michael R.
• Assistant Examiner(s): AUVE, GLENN ALLEN
• Application Number:
  US07/882,765
• Time in Patent Office: 498 Days
• Field of Search: 395/275, 395/425, 395/325, 395/250, 395/200, 371/12, 371/10.1, 371/10.2, 371/21.1, 364/134, 364/228.1, 364/243, 364/243.1, 364/256.3, 364/256.6, 364/DIG. 1, 364/931.46, 364/DIG. 2
• US Class Current: 710/21
• CPC Class Codes: G06F 11/16 Error detection or correction of the data by redundancy in hardware
• CPC Class Codes: G06F 11/2071 using a plurality of controllers

Abstract

A method and apparatus for transferring data between two storage media, and is used in an illustrative embodiment to transfer data between two storage media in a shadow set, the storage media being accessible to one or more host processors. The method of the preferred embodiment includes the steps of: A. receiving a command from one of the host processors, the command specifying data to be transferred from a first storage medium to a second storage medium; B. transferring the data specified in the command received from the host from the first storage medium to the second storage medium in a series of subtransfers, each of the subtransfers transferring a portion of the data; and C. processing one or more I/O requests to the shadow set received from one or more host processors by, for each received I/O request: a. implementing the I/O request if the I/O request does not involve a section of the shadow set currently involved in one of the subtransfers; and b. stalling the I/O request if the I/O request involves a section of said shadow set currently involved in one of the subtransfers, and implementing the I/O request when the subtransfer has completed.

Claims

1. A method of transferring data between two storage media in a shadow set of storage media accessible by one or more hose processors for I/O requests, said method comprising the steps of:

A. receiving a command from one of said host processors, said command specifying data to be transferred from a first said storage medium to a second said storage medium;

B. transferring said data specified in said command from said first storage medium to said second storage medium in a series of subtransfers, each of said subtransfers transferring a portion of said specified data; and

C. processing one or more I/O requests received from said host processors for access to said shadow set by, for each received I/O request;

a. implementing said I/O request if said I/O request does not involve a section of said shadow set currently involved in one of said subtransfers; and

b. stalling said I/O request if said I/O request involves a section of said shadow set currently involved in one of said subtransfers, and implementing said I/O request when said one of said subtransfers has completed.

2. The method of claim 1 further comprising stalling a said subtransfer that has not yet begun if said subtransfer involves a section of said shadow set which is currently involved in one of said I/O requests, and implementing said subtransfer when said one of said I/O requests has completed.

3. The method of claim 1 further comprising causing each of said hosts to transmit each said I/O request first to said first storage medium and, after said I/O request to said first storage medium has completed, then to said second storage medium.

4. The method of claim 1 further comprising receiving said command from said one of said host processors by a processor that manages access to said second storage medium.

5. The method of claim 4 further comprising causing said processor that manages access to said second storage medium to transmit commands to a processor that manages access to said first storage medium, said commands controlling said subtransfers.

6. The method of claim 5 wherein said commands sent from said processor that manages access to said second storage medium to said processor that manages access to said first storage medium specify an address in said first storage medium of said data to be transferred.

7. The method of claim 1 wherein each of said storage media is accessible by a plurality of host processors.

8. The method of claim 7 further comprising allowing said plurality of host processors to simultaneously access one or more of said storage media.

9. The method of claim 1 further comprising causing each of said host processors to maintain a table including information relating to said data transfer.

10. The method of claim 1 wherein each of said storage media is supported by a processor that manages access thereto, and further comprising controlling said subtransfers with said processors.

11. The method of claim 10 wherein each of said storage media is supported by a different processor.

12. The method of claim 1 wherein said storage media are disk storage devices.

13. A method of transferring data from a first storage device to a second storage device, said first storage device and said second storage device respectively comprising first and second storage media and first and second processors and being accessible to one or more host processors for I/O operations to said storage media, said method comprising the steps of:

(a) transmitting a first command from a said host processor to said first processor, said command specifying data to be transferred from one of said storage media to another one of said storage media;

(b) issuing a second command from said first processor to said second processor;

(c) transmitting said data from said one of said storage media to another one of said storage media in accordance with said second command; and

(d) controlling said transmitting of said data with said first and second processors.

14. A method of transferring data between two storage media in a shadow set of storage media accessible by one or more host processors for I/O requests, said method comprising the steps of:

A. receiving a command from one of said host processors, said command specifying data to be transferred from a first said storage medium to a second said storage medium;

B. transferring said data from said first storage medium to said second storage medium in response to said command; and

C. when said transferring is occurring, causing each of said host processors to transmit each said I/O request first to said first storage medium and, after said I/O request to said first storage medium has completed, then to said second storage medium, and thereafter allowing said host processors to transmit each said I/O request to said first storage medium and said second storage medium in any order.

15. An apparatus for transferring data between two storage media in a shadow set of storage media accessible by one or more host processors for I/O requests, said apparatus comprising:

a processor that manages access to a first said storage medium and operative to receive a command from one of said host processors, said command specifying data to be transferred between said first storage medium and a second said storage medium;

means responsive to said processor that manages access to said first storage medium for transferring said data specified in said command between said first storage medium and said second storage medium in a series of substransfers, each of said subtransfers transferring a portion of said specified data; and

means for processing one or more I/O requests received from said host processors for access to said shadow set by, for each received I/O request;

a. implementing said I/O request if said I/O request does not involve a section of said shadow set currently involved in one of said subtransfers being performed by said means for transferring; and

b. stalling said I/O request if said I/O request involves a section of said shadow set currently involved in one of said subtransfers, and implementing said I/O request when said one of said subtransfers has completed.

16. The apparatus of claim 15 wherein said means for transferring transfers said data from said second storage medium to said first storage medium.

17. The apparatus of claim 15 further comprising a processor that manages access to said second storage medium, and operative to receive commands from said processor that manages access to said first storage medium.

18. The apparatus of claim 17 wherein said processor supporting said second storage medium is operative to control said subtransfers in response to said commands.

19. The apparatus of claim 17 wherein said commands received by said processor supporting said second storage medium from said processor supporting said first storage medium specify an address in said second storage medium of said data to be transferred.

20. The apparatus of claim 15 wherein said means for transferring stalls a said subtransfer that has not yet begun if said subtransfer involves a section of said shadow set which is currently involved in one of said I/O requests, said means for transferring implementing said subtransfer when said one of said I/O requests has completed.

21. The apparatus of claim 15 wherein each of said host processors includes means for sending each said I/O request first to said second storage medium and, after said I/O request to said second storage medium has completed then to said first storage medium.

22. The apparatus of claim 15 wherein each of said storage media is accessible by a plurality of said host processors.

23. The apparatus of claim 22 wherein said plurality of host processors can simultaneously access one or more of said storage media.

24. The apparatus of claim 15 wherein each of said host processors maintains a table including information relating to said data transfer.

25. The apparatus of claim 15 wherein said storage media are disk storage devices.

26. An apparatus for transferring data between a first storage medium and a second storage medium, said storage media being accessible by one or more host processors for I/O operations to said storage media, said apparatus comprising:

a first processor that manages access to said first storage medium and operative to receive a command from one of said host processors, said command specifying data to be transferred between said storage media;

a second processor that manages access to said second storage medium and operative to receive a second command from said first processor; and

means controlled by said first processor and said second processor for transferring said specified data between said first storage medium and said second storage medium in accordance with said second command.

27. The apparatus of claim 26 wherein said storage media comprises a shadow set of storage media and said data is transferred between said storage media in a series of subtransfers, each of said subtransfers transferring a portion of said data, said apparatus further comprising:

means for processing one or more I/O requests received from said host processors for access to said storage media by, for each received I/O request;

a. implementing said I/O request if said I/O request does not involve a section of said shadow set currently involved in one of said subtransfers; and

b. stalling said I/O request if said I/O request involves a section of said shadow set currently involved in one of said subtransfers, and implementing said I/O request when said one of said subtransfers has completed.

28. The apparatus of claim 26 wherein said means for transferring transfers said data from said second storage medium to said first storage medium.

29. The apparatus of claim 28 wherein each of said hosts includes means for sending each said I/O request first to said second storage medium and, after said I/O request to said second storage medium has completed, then to said first storage medium.

30. The apparatus of claim 26 wherein each of said storage media is accessible by a plurality of said host processors.

31. The apparatus of claim 30 wherein said plurality of host processors can simultaneously access one or more of said storage media.

32. The apparatus of claim 26 wherein each of said host processors maintains a table including information relating to said data transfer.

33. The apparatus of claim 26 wherein said commands received by said second processor from said first processor specify an address in said second storage medium of said data to be transferred.

34. An apparatus for transmitting data stored in a storage medium, said storage medium being accessible by one or more host processors for I/O requests, said apparatus comprising:

a processor that manages access to said storage medium and operative to receive a command specifying data to be transmitted from said storage medium;

means responsive to said processor that manages access to said storage medium for transmitting said data specified in said command in a series of transmissions, each of said transmissions transmitting a portion of said specified data; and

means for processing one or more I/O requests received from said host processors for access to said storage medium by, for each received I/O request;

a. implementing said I/O request if said I/O request does not involve a section of said storage medium currently involved in one of said transmissions being performed by said means for transmitting; and

b. stalling said I/O request if said I/O request involves a section of said storage medium currently involved in one of said transmissions, and implementing said I/O request when said one of said transmissions has completed.

35. The apparatus of claim 34 wherein said means for transmitting transmits said data for receipt by a second storage medium.

36. The apparatus of claim 34 wherein said means for processing stalls a said transmission that has not yet begun if said transmission involves a section of said storage medium which is currently involved in one of said I/O requests, said means for processing implementing said transmission when said one of I/O requests has completed.

37. The apparatus of claim 34 wherein said storage medium is accessible by a plurality of said host processors.

38. The apparatus of claim 34 wherein said processor that manages access to said storage medium receives said command from one of said host processors.

39. The apparatus of claim 34 wherein said processor that manages access to said storage medium receives said command from a controller that supports a second storage medium.

40. The apparatus of claim 34 wherein said storage medium is one member in a shadow set of storage media, said means for transmitting sending said specified data to another member of said shadow set.