System and method for restoring previously backed-up data in a mass storage subsystem

• US 6,424,999 B1
• Filed: 03/11/1999
• Issued: 07/23/2002
• Est. Priority Date: 03/11/1999
• Status: Expired due to Term

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Arnon, Dan, Ofek, Yuval
• Primary Examiner(s): Sheikh, Ayaz
• Assistant Examiner(s): Duong, Oanh
• Application Number:
  US09/268,494
• Time in Patent Office: 1,230 Days
• Field of Search: 709/208, 709/200, 709/227, 709/232, 709/209, 709/620, 711/161, 711/162, 707/8, 707/202, 707/3, 707/200-206, 340/825.54, 364/200
• US Class Current: 709/208
• CPC Class Codes: G06F 11/1469 Backup restoration techniques
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

A system comprising a mass storage subsystem, as a master device and backup subsystem, as a slave device, the slave device transferring data items to the master device during a restore operation. Each data item to be restored is identified by a data item identifier. The master device initially provides the slave device with a list of data item identifiers and the slave device receives the data item identifier list from the master device and order the data item identifiers thereon in an optimal order for transfer to the master device, the ordering based on the ordering of the data items on storage media on which they are stored. The master device, in each of a plurality of iterations, receives from the slave device data item identifiers identifying a data item transferred during a previous iteration and a data item to be transferred during the current iteration and requests the slave device to transfer the data item to be transferred. The master device uses the data item identifier that it receives from the slave device identifying the data item transferred during the previous iteration to confirm that the data item corresponded to the data item that was to have been transferred during the previous iteration. The slave device, in each iteration, provides the master device with the data item identifiers identifying the data item transferred during the previous iteration and the data item to be transferred during the current iteration, and transfers the data item to be transferred during the iteration to the master device when requested by the master device.

Claims

1. A system comprising:

A. a mass storage subsystem as a master device and a back-up subsystem as a slave device,

B. the slave device transferring data items to the master device to perform a restore operation, each data item being identified by a data item identifier,

C. the master device being configured to, in each of a plurality of iterations, receive from the slave device data item identifiers identifying a data item transferred during a previous iteration and a data item to be transferred during the current iteration and to request the slave device to transfer the data item to be transferred, the master device being further configured to use the data item identifier that it receives from the slave device identifying the data item transferred during the previous iteration to confirm that the data item corresponded to the data item that was to have been transferred during the previous iteration; and

D. the slave device being configured to, in each iteration, provide the master device with the data item identifiers identifying the data item transferred during the previous iteration and the data item to be transferred during the current iteration and transfer the data item to be transferred during the iteration to the master device when requested by the master device.

2. A system as defined in claim 1 in which in each iteration

A. the master device, after receiving the data item identifier from the slave device identifying the data item to be transferred during the iteration, transfers the data item identifier to the slave device; and

B. the slave device uses the data item identifier received from the master device in connection with selection of the data item for transfer when requested by the master device.

3. A system as defined in claim 1 in which

A. the master device is further configured to initially provide the slave device with a list of data item identifiers and to thereafter control the transfer of data from the slave device to the master device in a plurality of iterations, and

B. the slave device is further configured to receive the data item identifier list from the master device and order the data item identifiers thereon in an order that it prefers for transfer to the master device.

4. A system as defined in claim 1 in which the slave device stores data items on a storage medium, the slave device being configured to retrieve each data item from the storage medium prior to transferring it to the master device, the slave device being further configured to order the data item identifiers from the list received from the master device in relation to an ordering of the data items on the storage medium.

5. A system as defined in claim 4 in which the storage medium stores data items for serial retrieval, the slave device being further configured to order the data item identifiers from the list received from the master device to optimize retrieval in relation to the ordering of the data items on the storage medium.

6. A system as defined in claim 5 in which the storage medium is a tape storage medium.

7. A system as defined in claim 1 in which the master device is configured to initiate a selected error recovery operation in connection with the slave device, if the master device determines, from the data item identifier that it receives from the slave device identifying the data item transferred during the previous iteration, that the data item does not correspond to the data item that was to have been transferred during the previous iteration.

8. A system as defined in claim 7 in which, in accordance with the selected error recovery operation, the slave device transfers the data item identified by the data item that was to have been transferred during the previous operation.

9. A method of controlling a mass storage subsystem as a master device and a back-up subsystem as a slave device during a restore operation to enable the slave device to transfer data items to the master device, each data item being identified by a data item identifier the method comprising the steps of, in each of a plurality of iterations:

A. enabling the master device to;

i. receive from the slave device data item identifiers identifying a data item transferred during the current iteration;

ii. request the slave device to transfer the data item to be transferred; and

iii. to use the data item identifier that it receives from the slave device identifying the data item transferred during the previous iteration to confirm that the data item corresponded to the data item that was to have been transferred during the previous iteration; and

B. enabling the slave device to;

i. provide the master device with the data item identifiers identifying the data item transferred during the previous iteration and the data item to be transferred during the current iteration; and

ii. transfer the data item to be transferred during the iteration to the master device when requested by the master device.

10. A method as defined in claim 9 further comprising the steps of, in which in each iteration:

A. enabling the master device, after receiving the data item identifier from the slave device identifying the data item to be transferred during the iteration, to transfer the data item identifier to the slave device; and

B. enabling the slave device to use the data item identifier received from the master device in connection with selection of the data item for transfer when requested by the master device.

11. A method as defined in claim 9 further comprising the steps of:

A. enabling the master device to initially provide the slave device with a list of data item identifiers and to thereafter control the transfer of data from the slave device to the master device in a plurality of iterations, and

B. enabling the slave device to initially receive the data item identifier list from the master device and order the data item identifiers thereon in an order that it prefers for transfer to the master device.

12. A method as defined in claim 9, the slave device storing data items on a storage medium with the slave device retrieving each data item from the storage medium prior to transferring it to the master device, the method further comprising the step of enabling the slave device to order the data item identifiers from the list received from the master device in relation to an ordering of the data items on the storage medium.

13. A method as defined in claim 12, the storage medium storing data items for serial retrieval, the method further comprising the step of enabling the slave device to order the data item identifiers from the list received from the master device to optimize retrieval in relation to the ordering of the data items on the storage medium.

14. A method as defined in claim 9 further comprising the step of, if the master device determines, from the data item identifier that it receives from the slave device identifying the data item transferred during the previous iteration, that the data item does not correspond to the data item that was to have been transferred during the previous iteration, enabling the master device to initiate a selected error recovery operation in connection with the slave device.

15. A method as defined in claim 14 in which the selected error recovery operation includes the step of enabling the slave device to transfer the data item identified by the data item that was to have been transferred during the previous operation.