Data transferring system having foreground and background modes and upon detecting significant pattern of access in foreground mode to change background mode control parameters

• US 5,896,548 A
• Filed: 02/28/1997
• Issued: 04/20/1999
• Est. Priority Date: 09/01/1995
• Status: Expired due to Term

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Ofek, Yuval
• Primary Examiner(s): Lee, Thomas C.
• Assistant Examiner(s): YUAN, CHIEN H
• Application Number:
  US08/807,452
• Time in Patent Office: 781 Days
• Field of Search: 711/114, 711/117, 395/182.05, 395/595, 395/823
• US Class Current: 710/20
• CPC Class Codes: G06F 12/0638 Combination of memories, e.g. ROM and RAM such as to permit replacement or supplementing of words in one module by words in another module address formation of the next microinstruction G06F9/26; masking faults in memories by using spares or by reconfiguring G11C29/70
• CPC Class Codes: G06F 12/08 in hierarchically structured memory systems, e.g. virtual memory systems
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache
• CPC Class Codes: G06F 3/0607 by facilitating the process of upgrading existing storage systems, e.g. for improving compatibility between host and storage device
• CPC Class Codes: G06F 3/0647 Migration mechanisms
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD
• CPC Class Codes: G11B 19/02 Control of operating function, e.g. switching from recording to reproducing
• CPC Class Codes: G11B 5/86 Re-recording, i.e. transcribing information from one magnetisable record carrier on to one or more similar or dissimilar record carriers by varying the order of the information G11B27/029, G11B27/036

Abstract

A method and apparatus for transferring data from a donor storage device to a target storage device in parallel with requests from a host computer for transfers between the host computer and the target storage device. A copy subroutine operates in response to background and foreground mode controllers. The background mode controller normally copies data from an initial position in the donor storage device sequentially by data block. When a DTR command from the host processor requests a data element from a block that has not migrated to the target storage device, the foreground controller uses the copy subroutine to transfer the designated block. The storage areas are divided into statistical blocks. If a threshold number of consecutive DTR commands accesses a particular statistical block, the system resets the parameters for the background mode controller to effectively move the copy subroutine to begin background copying from the statistical block. A subsequent request to move the subroutine in the background mode cannot occur until a minimum number of data blocks have been transferred.

Claims

1. A method for transferring blocks of data elements from storage locations in a first data storage device to storage locations in a second data storage device wherein a host computer generates data transfer requests for data elements from arbitrary storage locations in the second data storage device, said method comprising the steps of:

A. defining a copy subroutine for effecting the transfer of data blocks in response to predetermined control parameters;

B. enabling a background mode controller to establish the predetermined control parameters for the copy subroutine;

C. enabling a foreground mode controller to make transfers of a data block in response to a data transfer request that accesses a data block located only in the first data storage device;

D. determining the existence of a significant pattern of accesses in response to data transfer requests from the host computer; and

E. altering the predetermined control parameters for the background mode controller in response to the occurrence of the significant pattern.

2. A method as recited in claim 1 wherein the second data storage device includes a flag corresponding to each data block having a first value indicating that the corresponding data block is located only in the first data storage device and wherein one of the predetermined control parameters is the address of a data block location, said copy subroutine including the steps of:

i. moving a data block from the first to the second data storage device when the corresponding flag is at the first value; and

ii. establishing a second value for the flag after the transfer is complete.

3. A method as recited in claim 1 wherein said copy subroutine includes the step of moving a data block from the first to the second data storage device.

4. A method as recited in claim 3 wherein said step of enabling a background mode controller includes the step of generating an initial address for a data block as an initial address parameter.

5. A method as recited in claim 4 wherein the second data storage device includes a flag corresponding to each data block having a first value indicating that the corresponding data block is located only in the first data storage device, said copy subroutine including the steps of:

i. altering the address parameter to identify a next data block in sequence if the corresponding flag has the first value; and

ii. establishing a second value for the flag.

6. A method as recited in claim 2 wherein said foreground mode controller responds to the receipt of a data transfer request by:

i. interrupting the operation of the background mode controller;

ii. calling the copy subroutine to effect the transfer of a block containing the requested data element; and

iii. restoring the background mode controller to its normal operation.

7. A method as recited in claim 6 wherein:

said step of determining the existence of a significant pattern includes the steps of;

i. dividing the available storage locations into contiguous localized areas wherein each localized area comprises a predetermined number of contiguous storage locations; and

ii. counting successive data transfer requests that access a given localized area for a predetermined number of consecutive instances;

said altering of the predetermined control parameters includes the step of setting an interruption flag; and

said background mode controller responds to the interruption flag by loading the address of the localized area.

8. A method as recited in claim 6

wherein said step of determining the existence of a significant pattern includes the steps of:

i. dividing the available storage locations into contiguous localized areas wherein each localized area comprises a predetermined number of contiguous storage locations; and

ii. counting successive data transfer requests that access a given localized area for a predetermined number of consecutive instances;

said altering of the predetermined control parameters includes the steps of setting an interruption flag;

said background mode controller responds to the interruption flag by loading the address of the localized area; and

said altering step additionally comprises;

i. monitoring the number of data transfers by the copy subroutine from a given set of predetermined control parameters; and

ii. setting the interruption flag only after a predetermined number of iterations of the copy subroutine have been performed.

9. A method as recited in claim 8 wherein said background mode controller increments the number of accesses each time it calls the copy subroutine.

10. A method for transferring a data block of data elements from storage locations in a first data storage device to storage locations in a second data storage device by copying data blocks from sequential storage locations in a non-redundant fashion beginning from a defined starting storage location wherein data transfer requests for data elements that access arbitrary storage locations can occur during the sequential copying, said method comprising the steps of:

A. defining a copy subroutine for effecting the transfer of data blocks in response to predetermined control parameters,

B. initializing the predetermined control parameters thereby to establish initial operations of the copy subroutine including the defined starting storage location,

C. defining a plurality of localized areas, each localized area corresponding to a predetermined number of consecutive data elements; and

D. thereafter and until all the data elements are copied to the second data storage device;

i. monitoring the data transfer requests for activity within a localized area constituting a significant activity; and

ii. setting the control parameters including the starting storage location to a storage location in the localized area when said monitoring determines significant activity in a localized area thereby to enable the copy subroutine to make transfers at the localized area.

11. A method as recited in claim 10 wherein each of the first and second data storage devices comprises a disk array storage device and each data block is constituted by a single track on a disk array storage device, said definition of the copy subroutine including the step of effecting the transfer of an entire track during each operation of the copy subroutine.

12. A method as recited in claim 11 wherein said initializing of predetermined control parameters additionally includes the step of defining a need migration flag for each track having a first value indicating that the data in a corresponding track is located only on the first data storage device, said step of defining the copy subroutine additionally including the step of establishing a second value for the need migration flag corresponding to a track that has been transferred.

13. A method as recited in claim 12 wherein one of the control parameters is a track address, said step of initializing the predetermined control parameters including setting the track address to an initial value and beginning the copy subroutine at the corresponding track.

14. A method as recited in claim 13 wherein one of control parameters is a statistical block size and said step of defining the plurality of localized areas includes the step of defining contiguous blocks of tracks, each block containing a number of tracks corresponding to the statistical block size.

15. A method as recited in claim 14 wherein said step of setting the control parameters includes the enabling steps of:

i. counting each request for access to a localized area; and

ii. comparing the number of consecutive requests for access to a single localized area to a predetermined threshold.

16. A method as recited in claim 15 wherein each localized area is identified by a starting address and said step of setting the control parameters upon detecting significant activity includes setting the address parameter for the copy subroutine to the starting address of the localized area in which the significant activity has occurred.

17. A method as recited in claim 16 wherein one of the control parameters is represents a minimum number of tracks to be copied and said enabling step includes the additional step of comparing the number of tracks that have been transferred from a localized area.

18. Apparatus for transferring blocks of data elements from storage locations in a first data storage device to storage locations in a second data storage device wherein a host computer generates data transfer requests for data elements from arbitrary storage locations in the second data storage device, said apparatus comprising:

A. a copy subroutine for effecting the transfer of data blocks in response to predetermined control parameters;

B. a background mode controller for establishing the predetermined control parameters for the copy subroutine;

C. foreground mode controller for transferring a data block in response to a data transfer request that accesses a data block located only in the first data storage device;

D. means for determining the existence of a significant pattern of accesses in response to data transfer requests from the host computer; and

E. means for altering the predetermined control parameters for said background mode controller in response to the occurrence of the significant pattern.

19. Apparatus as recited in claim 18 wherein the second data storage device includes a flag corresponding to each data block having a first value indicating that the corresponding data block is located only in the first data storage device and wherein one of the predetermined control parameters is the address of a data block location, said copy subroutine including:

i. means for moving a data block from the first to the second data storage device when the corresponding flag is at the first value; and

ii. means for establishing a second value for the flag after the transfer is complete.

20. Apparatus as recited in claim 18 wherein said copy subroutine includes means for moving a data block from the first to the second data storage device.

21. Apparatus as recited in claim 20 wherein said background mode controller includes means for generating an initial address for a data block as an initial address parameter.

22. Apparatus as recited in claim 21 wherein the second data storage device includes a flag corresponding to each data block having a first value indicating that the corresponding data block is located only in the first data storage device, said copy subroutine including:

i. means for altering the address parameter to identify a next data block in sequence if the corresponding flag has the first value; and

ii. means for establishing a second value for the flag after the data block is transferred.

23. Apparatus as recited in claim 19 wherein said foreground mode controller includes:

i. means for interrupting the operation of the background mode controller in response to the receipt of a data transfer request;

ii. means for operating said copy subroutine to effect the transfer of a block containing the requested data element; and

iii. means for restoring said background mode controller to its normal operation.

24. Apparatus as recited in claim 23 wherein said means for determining the existence of a significant pattern includes:

i. means for dividing the available storage locations into contiguous localized areas wherein each localized area comprises a predetermined number of contiguous storage locations; and

ii. means for counting successive data transfer requests that access a given localized area for a predetermined number of consecutive instances;

said altering means includes means for setting an interruption flag; and

said background mode controller includes means responsive to the interruption flag for loading the address of the localized area.

25. Apparatus as recited in claim 23 wherein said means for determining the existence of a significant pattern includes:

i. means for dividing the available storage locations into contiguous localized areas wherein each localized area comprises a predetermined number of contiguous storage locations; and

ii. means for counting successive data transfer requests that access a given localized area for a predetermined number of consecutive instances;

said background mode controller includes means responsive to the interruption flag for loading the address of the localized area; and

said altering means comprises;

i. means for setting an interruption flag;

ii. monitoring the number of data transfers by the copy subroutine from a given set of predetermined control parameters; and

iii. setting the interruption flag only after a predetermined number of iterations of the copy subroutine have been performed.

26. Apparatus as recited in claim 25 wherein said background mode controller includes means incrementing the number of accesses each time it calls the copy subroutine.

27. Apparatus for transferring a data block of data elements from storage locations in a first data storage device to storage locations in a second data storage device by copying data blocks from sequential storage locations in a non-redundant fashion beginning from a defined starting storage location wherein data transfer requests for data elements the access arbitrary storage locations can occur during the sequential copying, said apparatus comprising:

A. a copy subroutine for effecting the transfer of data blocks in response to predetermined control parameters,

B. means for initializing the predetermined control parameters thereby to establish initial operations of the copy subroutine including the defined starting storage location,

C. means for defining a plurality of localized areas, each localized area corresponding to a predetermined number of consecutive data elements; and

D. means thereafter and until all the data elements are copied to the second data storage device for effecting a data transfer including;

i. means for monitoring the data transfer requests for activity within a localized area constituting a significant activity; and

ii. means for setting the control parameters including the starting storage location to a storage location in the localized area when said monitoring means determines significant activity in a localized area thereby to enable the copy subroutine to make transfers at the localized area.

28. Apparatus as recited in claim 27 wherein each of the first and second data storage devices comprises a disk array storage device and each data block is constituted by a single track on a disk array storage device, said copy subroutine including means for effecting the transfer of an entire track during each operation of said copy subroutine.

29. Apparatus as recited in claim 28 additionally including a need migration flag for each track having a first value indicating that the data in a corresponding track is located only on the first data storage device, said copy subroutine including means for establishing a second value for the need migration flag corresponding to a track that has been transferred.

30. Apparatus as recited in claim 29 wherein one of the control parameters is a track address, said initializing means setting the track address to an initial value to begin said copy subroutine at the corresponding track.

31. Apparatus as recited in claim 30 wherein one of control parameters is a statistical block size and said defining means includes means for defining contiguous blocks of tracks, each block containing a number of tracks corresponding to the statistical block size.

32. Apparatus as recited in claim 31 wherein said setting means includes:

i. means for counting each request for access to a localized area; and

ii. means for comparing the number of consecutive requests for access to a single localized area to a predetermined threshold.

33. Apparatus as recited in claim 32 wherein each localized area is identified by a starting address and said setting means includes means for setting the address parameter for said copy subroutine to the starting address of the localized area in which the significant activity has occurred.

34. Apparatus as recited in claim 33 wherein one of the control parameters is represents a minimum number of tracks to be copied and said enabling means includes means for comparing the number of tracks that have been transferred from a localized area.