Method and apparatus for independent and simultaneous access to a common data set

• US 6,370,626 B1
• Filed: 04/30/1999
• Issued: 04/09/2002
• Est. Priority Date: 04/30/1999
• Status: Expired due to Term

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Vishlitzky, Natan, Kopylovitz, Haim, Ofek, Yuval, Gagne, Mathieu
• Primary Examiner(s): Yoo, Do Hyun
• Assistant Examiner(s): Namazi, Mehdi
• Application Number:
  US09/303,242
• Time in Patent Office: 1,075 Days
• Field of Search: 711/117-118, 711/162, 711/168, 711/154, 710/39, 710/52, 714/6
• US Class Current: 711/154
• CPC Class Codes: G06F 11/1451 by selection of backup contents
• CPC Class Codes: G06F 11/2069 Management of state, configuration or failover
• CPC Class Codes: G06F 11/2082 Data synchronisation
• CPC Class Codes: G06F 3/0613 in relation to throughput
• CPC Class Codes: G06F 3/065 Replication mechanisms
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]

Abstract

A method and apparatus for enabling a common data set to be utilized by multiple data processes. During a first operating mode, first and second data stores in a data storage facility with a common buffer attach to a first data process and act as mirrors. Data to be written transfers to the common buffer and then to the data stores. A second command produces a split whereby the first data store remains attached to the first data process and the second data store is available to the second data process. After the second command is executed, any data in the common buffer is transferred to the corresponding data stores in parallel with and transparently to the actions between the first and second data processes and the first and second data stores, respectively.

Claims

1. A data storage facility for enabling the manipulation of common data by first and second data processes comprising:

A) first and second data stores and a buffer connected thereto, a write request from a data process identifying a specific location being transferred to said buffer as a pending write request with the data associated, the pending write request thereafter being transferred from said buffer to the specified location in a corresponding data store, and

B) a control for said data storage facility including;

i) a first controller for transferring the operation of the storage facility from a first operating mode during which said second data store acts as a mirror for said first data store that interacts with the first data process to a second operating mode during which said second data store ceases to act as a mirror and interacts with the second data process, and

ii) a second controller responsive to said first controller that controls the processing of all pending write requests at the time said first controller makes the transfer to the second operating mode, said second controller operating in parallel with and transparently to the interaction between said first and second data stores with the first and second data processes, respectively.

2. A data storage facility as recited in claim 1 wherein each of said data stores has addressed locations and said second controller includes:

i) a first module that operates in parallel with and asynchronously with respect to operations between the data processes and their respective data stores for processing any pending write operations in said buffer in an ordered fashion, and

ii) a second module that operates in response to a predetermined data transfer request to an addressed location from the first and second data processes for processing any pending write operation in an area of said buffer that is assigned to that addressed location.

3. A data storage facility as recited in claim 2 wherein the predetermined data transfer requests include write commands from the first and second data processes and read commands from the second data process, said second module including a decoder for such data transfer requests.

4. A data storage facility as recited in claim 3 wherein said data storage facility includes, for each data store and for each addressed location in said data store, a table of flags including at least one write-pending flag that identifies each write request pending in said buffer and a second flag indicating that specific track to be processed by said second module.

5. A data storage facility as recited in claim 4 including additional flags and a control means for monitoring the status of said write pending flags for controlling the state of said additional flags, said control means being responsive to each of said first and second modules.

6. A data storage facility as recited in claim 5 wherein said control means includes a decoder responsive to the write pending flags for determining whether said control unit module requires a duplicate pending write entry in said buffer and a generator that produces the duplicate cache slot.

7. A data storage facility for controlling data transfers in a data processing system with first and second data processes and a data storage facility with first and second data stores and a buffer connected thereto, the data storage facility responding to a predetermined transfer request by transferring data to a write pending location in the buffer and thereafter transferring the data to the data stores whereby during a first operating mode the first and second data stores act as mirror memories, said data storage facility additionally comprising:

A) a first controller responsive to a predetermined command for connecting the second data store for operation with the second data process in parallel with continued operations between the first data store and the first data process whereby the second data store is isolated from the first data process,

B) a first list, maintained during the first operating mode that identifies all write pending locations for data to be transferred from the buffer to the second data store,

C) a second list of all write pending locations for data to be transferred to the second data store upon the establishment of the second operating mode, and

D) a second controller responsive to the transfer to the second operating mode for responding to data transfer requests for data in a write pending data location in the second list in either of the first and second data stores by effecting a transfer of the data to the second data store.

8. A method for enabling first and second data processes to manipulate common data in a data storage facility comprising the steps of:

A) defining first and second data stores and a buffer connected thereto, a write request from one of said data processes identifying a specific location being transferred to the buffer as a pending write request with the data associated with the pending write request thereafter being transferred from the buffer to the specified location in a corresponding data store,

B) establishing a first operating mode during which the second data store acts as a mirror for the first data store that interacts with the first data process,

C) transferring the operation of the storage facility from the first operating mode to a second operating mode during which the second data store interacts with the second data process and ceases to act as mirror for the first data store, and

D) during the second operating mode controlling the processing of all pending write requests at the time the first controller makes the transfer to the second operating mode, said pending write request controlling step operating in parallel with and transparently to the interaction between the first and second data stores with the first and second data processes, respectively.

9. A method as recited in claim 8 wherein each of the data stores has addressed locations and the transfer to the second operating mode enables:

i) a first processing of any pending write operations in the buffer in an ordered fashion in parallel with and asynchronously with respect to operations between the data processes and their respective data stores, and

ii) in response to a predetermined data transfer request to an addressed location from the first and second data processes a second processing of any pending write operation in an area of the buffer that is assigned to that addressed location.

10. A method as recited in claim 9 wherein the predetermined data transfer requests include write commands from the first and second data processes and read commands from the second data process, said second processing including the step of decoding data transfer requests for the predetermined requests.

11. A method as recited in claim 10 wherein the data storage facility includes, for each data store and for each addressed location in the data store, a table of flags including at least one write-pending flag that identifies each write request pending in the buffer and a second flag indicating that specific track to be processed by the second processing, each write data transfer request normally transferring the request to the buffer and updating a corresponding write-pending flag.

12. A method as recited in claim 11 wherein the table of flags includes additional flags, updating the state of the additional flags in response to the status of the write pending flags, said first and second processing steps enabling said updating of said additional flags.

13. A method as recited in claim 12 including the additional step of generating a duplicate cache slot in response to predetermined states of the write pending flags.

14. A method for controlling data transfers in a data processing system with first and second data processors and a data storage facility with first and second data stores and a buffer connected thereto, the data storage facility responding to a predetermined transfer request by transferring data to a write pending location in the buffer and thereafter transferring the data to the data stores whereby during a first operating mode the first and second data stores act as mirror memories, said method being initiated upon receipt of a predetermined command for connecting the second data store for operation with the second data processor in parallel with continued operations between the first data store and the first data processor, said method comprising the steps of:

A) maintaining, during the first operating mode, an identification of all write pending locations for data to be transferred from the buffer to the second data store,

B) establishing a temporary operating mode in response to the predetermined command to connect the second data store to operate with the second processor and isolate the second data store from the first processor,

C) establishing a list of all write pending locations for data to be transferred to the second data store upon the establishment of the temporary operating mode, and

D) during the balance of the temporary operating mode responding to data transfer requests for data in a write pending data location in the list in either of the first and second data stores by effecting a transfer of the data to the second data store.

15. A data storage facility for enabling the manipulation of common data by first and second data processes comprising:

A) first and second data stores and a buffer, a write request from a data process identifying a specific location being transferred to said buffer as a pending write request with the data associated with the pending write request thereafter being transferred to the specified location a corresponding data store, and

B) a first controller for transferring operations from a first operating mode during which said second data store acts as a mirror for said first data store that interacts with the first data process to a second operating mode during which said second data store interacts with the second data process, and

C) a second controller responsive to said first controller that controls the processing of all pending write requests at the time said first controller makes the transfer to the second operating mode, said second controller operating in parallel with and transparently to the interaction between said first and second data stores with the first and second data processes, respectively.

16. Data storage as recited in claim 15 wherein each of said data stores has addressed locations and said second controller includes:

i) a first module that operates in parallel with and asynchronously with respect to operations between the data processes and their respective data stores for processing any pending write operations in said buffer in an ordered fashion, and

ii) a second module that operates in response to a predetermined data transfer request to an addressed location from the first and second data processes for processing any pending write operation in an area of said buffer that is assigned to that addressed location.

17. Data storage as recited in claim 16 wherein the predetermined data transfer requests include write commands from the first and second data processes and read commands from the second data process, said second module including a decoder for such data transfer requests.

18. Data storage as recited in claim 17 comprising, for each data store and for each addressed location in said data store, a table of flags including at least one write-pending flag that identifies each write request pending in said buffer and a second flag indicating that specific track to be processed by said second module.

19. Data storage as recited in claim 18 including additional flags and a control means for monitoring the status of said write pending flags for controlling the state of said additional flags, said control means being responsive to each of said first and second modules.

20. A data storage facility as recited in claim 19 wherein said control means includes a decoder responsive to the write pending flags for determining whether said control means requires a duplicate pending write entry in said buffer and a generator that produces the duplicate pending write entry.

21. Data storage with means for controlling data transfers in response to first and second data processes and with first and second data stores and a buffer for responding to a predetermined transfer request by transferring data to a write pending location in the buffer and thereafter transferring the data to the data stores whereby during a first operating mode the first and second data stores act as mirror memories, said data storage additionally comprising:

A) a first controller responsive to a predetermined command for connecting the second data store for operation with the second data process in parallel with continued operations between the first data store and the first data process,

B) a first list, maintained during the first operating mode that identifies all write pending locations for data to be transferred from the buffer to the second data store,

C) a second list of all write pending locations for data to be transferred to the second data store upon the establishment of the second operating mode, and D) a second controller responsive to the transfer to the second operating mode for responding to data transfer requests for data in a write pending data location in the second list in either of the first and second data stores by effecting a transfer of the data to the second data store.

22. A method for enabling first and second data processes to manipulate common data comprising the steps of:

A) defining first and second data stores and a buffer, a write request from one of said data processes identifying a specific location being transferred to the buffer as a pending write request with the data associated with the pending write request thereafter being transferred to the specified location in a corresponding data store,

B) establishing a first operating mode during which the second data store acts as a mirror for the first data store that interacts with the first data process,

C) transferring the operation of the storage facility from the first operating mode to a second operating mode during which the second data store interacts with the second data process and ceases to act as mirror for the first data store, and

D) during the second operating mode controlling the processing of all pending write requests at the time the first controller makes the transfer to the second operating mode, said pending write request controlling step operating in parallel with and transparently to the interaction between the first and second data stores with the first and second data processes, respectively.

23. A method as recited in claim 22 wherein each of the data stores has addressed locations and the transfer to the second operating mode enables:

i) a first processing of any pending write operations in the buffer in an ordered fashion in parallel with and asynchronously with respect to operations between the data processes and their respective data stores, and

ii) in response to a predetermined data transfer request to an addressed location from the first and second data processes a second processing of any pending write operation in an area of the buffer that is assigned to that addressed location.

24. A method as recited in claim 23 wherein the predetermined data transfer requests include write commands from the first and second data processes and read commands from the second data process, said second processing including the step of decoding data transfer requests for the predetermined requests.

25. A method as recited in claim 24 including the step of producing for each data store and for each addressed location in the data store, a table of flags including at least one write-pending flag that identifies each write request pending in the buffer and a second flag indicating that specific track to be processed by the second processing, each write data transfer request normally transferring the request to the buffer and updating a corresponding write-pending flag.

26. A method as recited in claim 25 wherein the table of flags includes additional flags, updating the state of the additional flags in response to the status of the write pending flags, said first and second processing steps enabling said updating of said additional flags.

27. A method as recited in claim 26 including the additional step of generating a duplicate cache slot in response to predetermined states of the write pending flags.

28. A method for controlling data transfers with first and second data processors and with first and second data stores and a buffer, said method responding to a predetermined transfer request by transferring data to a write pending location in the buffer and thereafter transferring the data to the data stores whereby during a first operating mode the first and second data stores act as mirror memories, said method being initiated upon receipt of a predetermined command for connecting the second data store for operation with the second data processor in parallel with continued operations between the first data store and the first data processor, said method comprising the steps of:

A) maintaining, during the first operating mode, an identification of all write pending locations for data to be transferred from the buffer to the second data store,

B) establishing a temporary operating mode in response to the predetermined command to connect the second data store to operate with the second processor and isolate the second data store from the first processor,

C) establishing a list of all write pending locations for data to be transferred to the second data store upon the establishment of the temporary operating mode, and

D) during the balance of the temporary operating mode responding to data transfer requests for data in a write pending data location in the list in either of the first and second data stores by effecting a transfer of the data to the second data store.