Data processing method and apparatus for enabling independent access to replicated data

• US 6,581,143 B2
• Filed: 05/09/2002
• Issued: 06/17/2003
• Est. Priority Date: 12/23/1999
• 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, Gagne, Mathieu
• Primary Examiner(s): Kim, Matthew
• Assistant Examiner(s): ELMORE, STEPHEN C
• Application Number:
  US10/142,164
• Publication Number:
  US 20020129203A1
• Time in Patent Office: 404 Days
• Field of Search: 711/162, 711/161, 711/144, 711/145, 707/10, 707/204, 714/5, 714/6
• US Class Current: 711/162
• CPC Class Codes: G06F 11/1451 by selection of backup contents
• CPC Class Codes: G06F 11/1469 Backup restoration techniques

Abstract

A data storage facility that allows data on a standard device to be replicated to other storage devices for independent and concurrent access. The standard device includes first and second tables for monitoring the operation of the standard device. The other storage device that receive the copies have tables that identify their status. The system utilizes these tables in various combinations to enable multiple copies to be altered and updated.

Claims

1. In a data processing system in which a first application program is adapted to interact with data in a first storage device located on a first physical disk storage unit, a control for enabling at least two additional programs to interact concurrently and independently with copies of the data stored in the first storage device, said control comprising:

A) device identification means for identifying additional storage devices on different physical disk storage units for each of the additional programs,

B) session reference means for defining a session reference for each of the additional storage devices, each session reference having entries for recording each change made to a corresponding portion of the data on the first storage device,

C) recording means for recording each change to a data portion on the first storage device in the corresponding entry of the session references,

D) device reference means for defining a device reference for each of the first and additional storage devices with entries for recording each change a respective program makes to a data portion,

E) copy generation means for generating independent copies of the data in the first storage device on the other storage devices for interaction with the respective additional programs,

F) device change recording means for recording in said device reference means each change each additional program makes to a data portion stored in its respective storage device,

G) updating means for updating data portions on a selected one of the additional storage devices on demand by combining the entries in said corresponding session and device references to identify changed data portions, and

H) copy means for copying the changed data portions from the first storage device to the selected storage device.

2. A control as recited in claim 1 wherein said copy generation means includes:

i) establishing means for establishing a session that identifies the first storage device and one of the additional storage devices as a selected storage device,

ii) synchronizing means for synchronizing the data an the selected storage device with the data on the first storage device, and

iii) splitting means, operable after achieving synchronism, for splitting the one additional storage device from the first storage device thereby to enable the interaction between the selected storage device and its corresponding program.

3. A control as recited in claim 2 wherein said splitting means includes means for marking as unchanged each entry in said session reference means tar the selected storage device and marking as valid each entry in the corresponding device reference means.

4. A control as recited in claim 2 wherein each entry in said device reference means has multiple entry sets for different storage devices and said splitting means includes:

i) first marking means for marking as invalid entries in one entry set of said device reference means that corresponds to another storage device that is a mirror for the selected storage device if a corresponding entry in said session reference means is marked as changed,

ii) second marking means for marking as valid entries in one entry set for said selected storage device corresponding to the first storage device, and

iii) third marking means for marking as unchanged all the entries in said session reference means.

5. A control as recited in claim 4 including a restoring means for restoring data to the first storage device from a selected storage device including:

i) fourth marking means for marking as invalid all the entries in one entry set in said device reference means for first storage device corresponding to said first storage device,

ii) fifth marking means for marking as valid all the entries in one entry set in said device reference means for the first storage device corresponding to the selected storage device,

iii) sixth marking means for marking as unchanged all the entries in said session reference means for the selected storage device, and

iv) seventh marking means for marking as changed all the entries in the others of said session reference means whereby data in the selected storage device restores the data in the first storage device and enables the subsequent transfer of data to any non-selected storage device.

6. A control as recited in claim 1 including restoring means for restoring the data in the first storage device limited to data that was changed in the first storage unit since a prior splitting of the first and the selected storage device, said restoring means including:

i) fourth marking means for marking as valid all the entries in one entry set in said device reference means for the first storage device corresponding to the selected storage device,

ii) fifth marking means for marking as invalid all the entries in one entry set in the first storage device corresponding to the first storage device if the corresponding entry in said device reference means for the selected storage device is valid or if the entry in the session reference means for the selected storage devices is changed,

iii) sixth marking means for marking as unchanged all the entries in said session reference means for the selected storage device, and

iv) seventh marking means for marking as changed all the entries in the other of said session reference means whereby only data portions corresponding to changed entries in the first and selected storage devices transfer to the first storage device and whereby the system is enabled to transfer restored data to any non-selected storage device.

7. A control as recited in claim 1 each said session reference means identifies the first storage device and a selected storage device and wherein each of the first and additional storage devices stores each data portion in a data track, said device reference means including entry defining means for defining a first entry set corresponding to itself and a second entry set corresponding to the other storage devices, each of said session reference and device reference means establishing a correspondence between corresponding entries and a track.

8. A control as recited in claim 7 wherein said copy generation means includes:

i) establishing means for establishing a session that identifies the first storage device and a selected storage device,

ii) synchronizing means tar synchronizing the data on the selected storage device with the data on the first storage device, and

iii) splitting means operable after achieving synchronism for splitting the selected storage device from the first storage device thereby to enable the interaction between the selected storage device and its corresponding program.

9. A control as recited in claim 8 wherein said splitting means includes means for marking as unchanged each track entry in said session reference means for the selected storage device and marking as valid the corresponding track entry in said device reference means.

10. A control as recited in claim 8 wherein said splitting means includes:

i) first marking means for marking as invalid in said device reference means for the selected storage device those track entries in the entry set for any mirroring storage device if the corresponding track entry in said session reference means for the selected storage device is changed,

ii) second marking means for marking as valid in said device reference means for the selected storage device, those track entries in the entry set for the first storage device, and

iii) third marking means for marking as unchanged all the track entries in said session reference mans for the selected storage device.

11. A control as recited in claim 7 including restoring means for restoring data to the first storage device from a selected one of the other storage devices, said restoring means including:

i) fourth marking means for marking as valid all the entries in the entry set in said device reference means for the first storage device corresponding to the selected other storage device,

ii) fifth marking means for marking as invalid all the track entries in the entry set in the first storage device that corresponds the first storage device,

iii) sixth marking means for marking as unchanged all the track entries in said session reference means for the selected storage device, and

iv) seventh marking means for marking as changed all the track entries in the others of said session reference means whereby data in the selected one of the additional storage devices restores the data in the first storage device.

12. A control as recited in claim 7 including restoring means for restoring data to the first storage device limited to data in tracks of the first and the selected storage devices that occurred since a prior splitting of the first and the selected storage devices, said restoring means including:

i) fourth marking means for marking as valid all track entries in the entry set for the device change reference for the first storage device corresponding to the selected storage device,

ii) fifth marking means for marking as invalid all the track entries in the entry set in the first storage device corresponding to itself if the corresponding track entry in said device reference means for the selected storage device is valid or if the track entry in said session reference means for the selected storage device is changed,

iii) sixth marking means for marking as unchanged all track entries in said session reference means for the selected storage device, and

iv) seventh marking means for marking as changed all the track entries in the other of said session reference means whereby only data portions corresponding to changed entries in the first and selected storage devices restore the data in the first storage device.

13. A control for a multi-processor data processing system including a data storage facility wherein one program operates with data in one data storage device, said control enabling multiple copies of the data on the one storage device to be made on each of additional data storage devices for operation with other programs, said control comprising:

A) means for defining a first buffer for each additional storage device on which a copy is to be made,

B) means for defining a second buffer for each additional data storage device and the one data storage device,

C) means for copying the data on the one data storage device to one of the additional data storage devices,

D) means for enabling an other program to interact with the data on the one additional data storage device independently of the data on the one data storage device,

E) first recording means for recording each change made by the one program to the data on the one data storage device in each of said first buffers,

F) second recording means for recording each change made by the program to its corresponding additional storage device in said corresponding second buffer,

G) means operable upon completion of the independent interaction for combining the information in said corresponding first and second buffers to identify data to be copied from the one data storage device to the one additional data storage device thereby to enable said copying means to copy data to the one additional data storage device so it reflects the data in the one data storage device.