Method and apparatus for performing point in time backup operation in a computer system

• US 5,857,208 A
• Filed: 05/31/1996
• Issued: 01/05/1999
• Est. Priority Date: 05/31/1996
• Status: Expired due to Term

• Current Assignee: EMC Corporation (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Ofek, Yuval
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): RONES, CHARLES
• Application Number:
  US08/656,036
• Time in Patent Office: 949 Days
• Field of Search: 395/180, 395/181, 395/441, 395/481, 395/601, 395/620, 395/182.04, 365/230.03, 711/200, 707/204, 707/202
• US Class Current: N/A
• CPC Class Codes: G06F 11/1451 by selection of backup contents
• CPC Class Codes: G06F 11/2082 Data synchronisation
• CPC Class Codes: Y10S 707/99953 Recoverability
• CPC Class Codes: Y10S 707/99955 Archiving or backup

Abstract

A data network with a remote data facility for providing redundant data storage and for enabling concurrent point-in-time backup operations. A local data processing system with a data facility stores a data base and processes applications. A second system, physically separated from the first system, includes a data facility that normally mirrors the data in the first system. In a backup mode, the second system is enabled to transfer data from its data facility to a backup facility concurrently with, but independently of, the operation of the first system. On completion of the backup operation, the second system reconnects with and synchronizes with the first system thereby to reestablish the mirroring operation of the second system.

Claims

1. In a data network including a first data processing system with a first host computer and a first data storage facility for processing application programs, including a second data processing system with a second host computer, a second data storage facility and a backup facility for providing a copy of the data in the second data storage facility on separate media, and including a communications link for interconnecting the first and second data processing systems, the second data processing system operating in a normal operating mode to mirror the first data storage facility by transferring data through the communications link and wherein each of the data storage facilities includes at least one disk storage device characterized by a plurality of tracks and by block data transfers having a one-track length, the improvement of a method for enabling the backup of the data in the network without interfering with the operation of the first data processing system, said method comprising the steps of:

(A) enabling from the second data processing system a backup operating mode by disabling transfers over the communications link and initiating a backup operation from the second data storage facility to the backup facility, the backup operation occurring in parallel with operations in the first data processing system

(B) recording, in the first data processing system, each transfer to the first data storage facility during the backup operating mode produced the first data processing system,

(C) converting, upon return from the backup operating mode to a normal operating mode, the recordings of each transfer into a list of changed tracks, and

(D) copying the data from each changed track of the first storage facility identified by the list of changed tracks to each corresponding track in the second date storage facility.

2. A method as recited in claim 1 wherein the communications link includes a link director in each of the first and second data processing systems for controlling transfers over the communications link and wherein the link director in the first data processing system performs said copying concurrently with the operation of the first data processing system.

3. A method as recited in claim 1 the first data processing system maintains, for each track in the first data storage facility, track status defined by a first field indicating the validity of the track in the first data processing system data storage facility and a second field indicating the validity of the corresponding track in the second data processing system data storage facility and wherein the recording of track identifications in the first data processing system includes responding to each change in the data on a track by setting the second field in the track status for the corresponding track to a value for invalid data.

4. A method for operating first and second data processing systems interconnected by a communications link, each data processing system being capable of independent operation and including a host computer and a data storage facility that stores data at predetermined locations in data blocks, the second data processing system including a data backup facility and, operating, during a normal operating mode, to mirror in the data storage facility of the second data processing system the data in the data storage facility of the first data processing system in response to a copy program, said method producing a point-in-time backup on the data backup facility and comprising the steps of:

(A) disabling the copy program thereby isolating the first and second data processing systems and enabling the first data processing system to continue its operations,

(B) initiating the operation of the backup facility at the second data processing system thereby producing a backup of the data in the data storage facility of the second data processing system,

(C) recording, at the first data processing system and during the backup operation, an identification of each data block in the data storage means of the first data processing system that changes as a result of the operation of the first data processing system, and

(D) enabling the copy program upon completion of the backup operation thereby copying data blocks from the data storage facility in the first data processing system to the data storage facility in the second data processing system corresponding to the recorded identifications in the first data processing system thereby reestablishing the second data processing system as a mirror of the first data processing system.

5. A method as recited in claim 4 wherein the communications link includes a first link director connected to the first data processing system and a second link director connected to the second data processing system and wherein the first link director performs said copying and wherein said copying occurs concurrently with operation of the first data processing system after the normal operating mode is established.

6. A method as recited in claim 5 wherein the first data processing system maintains data block validity status that, for each data block, includes a first field indicating the validity of the data block in the first data processing system data storage facility and a second field indicating the validity of the data block in the second data processing system data storage facility and wherein the recording of data block identifications in the first data processing system includes the step of responding to each change in a data block produced by the first data processing system by setting the second field in the corresponding data block validity status to a value that indicates invalid data.

7. A method as recited in claim 6 wherein each of the data block status fields comprises a single bit having first and second states when the corresponding data is valid and invalid, respectively, and wherein said copying step includes converting the status of the second bits at the second state into a list of data blocks that had been changed by the first data processing system during the backup operation.

8. In a data processing network including first and second data processing systems interconnected by a communications link, each System being capable of independent operation and including a host computer and a data storage facility that stores data at predetermined locations in data blocks, said second data processing system additionally including a backup facility and, during a normal operating mode, operating to mirror the data in said data storage facility of said first data processing system, the improvement of:

(A) mode control means in said second data processing system for establishing the normal operating mode and for establishing a backup operating mode by disabling transfers through said communications link and enabling said backup facility in said second data processing system and enabling said first data processing system to continue its operations,

(B) recording means in said first data processing system for recording an identification of each data block in said data storage means of said first data processing system that changes as a result of the operation of said first data processing system,

(C) copying means at said communications link for copying data blocks from said data storage facility in said first data processing system to the data storage facility in said second data processing system, the data blocks corresponding to the recorded identifications in said first data processing system after said mode control means reestablishes the normal operating mode thereby to reestablish said second data processing system as a mirror of said first data processing system.

9. A network as recited in claim 8 wherein said first data processing system includes, for each data block, a data block status register means defined by a first field indicating the validity of the data block in said first data processing system data storage facility and a second field indicating the validity of the data block in said second data processing system data storage facility, said recording means responds to each change in a data block produced by said first data processing system by setting said second field in said corresponding data block validity status to a value indicating invalid data.

10. A network as recited in claim 9 wherein said copying means includes means for generating a changed track list in response to the track status registers with the second fields indicating invalid data thereby to identify all data blocks in said second data processing system that fail to mirror corresponding blocks in said first data processing system, said copying means being responsive to said changed track list by copying each of said identified data blocks from said data storage facility of said first data processing system to said data storage facility of said second data processing system.

11. A network as recited in claim 10 wherein each of said data block status register fields comprises a single bit having first and second states when the corresponding data is valid and invalid, respectively.

12. In a data network including a first data processing system with a first host computer and a first data storage facility for processing application programs, including a second data processing system with a second host computer, a second data storage facility and a backup facility for providing a backup copy of data in the second data storage facility on separate storage media and including a communications link for interconnecting said first and second data processing systems for normal operation wherein said second data processing system operates to mirror said first data storage facility by transferring data through said communications link and wherein each of said data storage facilities includes at least one disk storage device characterized by a plurality of tracks and by block data transfers having a one-track length, the improvement of a method whereby said backup facility is enabled to backup the data in the network without interfering with the operation of the first data processing system, the improvement comprising:

(A) mode control means in said second data processing system for establishing the normal operating mode and for establishing a backup mode for enabling said backup facility in said second data processing system to backup data in said second data storage facility while enabling the first data processing system to continue its operations,

(B) status registers in said first data processing system for recording each transfer to said first data storage facility during the backup operating mode produced by said applications programs in said first data processing system,

(C) means in said first data processing system for converting, upon return to a normal operating mode, the recordings of each transfer into a changed track list, and

(D) means for thereafter copying to each track in said second data storage facility the data from each track of said first storage facility identified by said changed track list.

13. A network as recited in claim 12 wherein the communications link includes a link director in each of said first and second data processing systems for controlling communications through said communications link and wherein said copying means operates in said link director in said first data processing system concurrently with the operation of said first data processing system.

14. A network as recited in claim 13 wherein said each track status register in said first data processing system includes a first field indicating the validity of data in a corresponding track in said first data processing system data storage facility and a second field indicating the validity of the data in the corresponding track in said second data processing system data storage facility, changes in the data of a track produced by an application program causing the setting of said second field in said corresponding track status register to a value indicating invalid data.

15. A network as recited in claim 14 wherein each of said track status register fields comprises a single bit having first and second states when the corresponding data is valid and invalid, respectively, said converting means producing the changed track list in response to track status registers in which the second field bit indicates a track in the second data storage facility with invalid data.