System executing log data transfer synchronously and database data transfer asynchronously

• US 20050210073A1
• Filed: 04/07/2004
• Published: 09/22/2005
• Est. Priority Date: 03/19/2004
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Oeda, Takashi, Kawamura, Nobuo, Yamaguchi, Kota
• Granted Patent: US 7,890,461 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 11/1471 involving logging of persistent data for recovery
• CPC Class Codes: G06F 11/2038 with a single idle spare processing component
• CPC Class Codes: G06F 11/2048 where the redundant components share neither address space nor persistent storage
• CPC Class Codes: G06F 11/2064 while ensuring consistency
• CPC Class Codes: G06F 11/2074 Asynchronous techniques
• CPC Class Codes: G06F 2201/80 Database-specific techniques

Abstract

A disaster recovery system and a method therefor, having: a function for receiving write requests from a host computer to write log information indicating the contents of a database process executed for a database buffer on a main site, database data updated on the database buffer and status information indicating the position of log information used for disaster recovery; a function for transferring the received write request for log information to a recovery site by a synchronous remote copy process; and a function for transferring the received write request for database data to the recovery site by an asynchronous remote copy process. While remote copy can be executed at a long distance without data loss, the deterioration of the performance of a database process on a main site can be suppressed.

Claims

1. A disaster recovery method for continuing a database process by changing an active database management system over to a standby database management system at the time of occurrence of a disaster, comprising the steps of:

receiving write requests from a host computer to write log information indicating the contents of a database process executed for a database buffer of said host computer, database data updated on said database buffer and status information indicating the position of log information used for disaster recovery;

updating log information, database data and status information in a main storage system in accordance with the contents of said received write requests;

transferring said received write requests for log information to a sub storage system of the standby database management system by a synchronous remote copy process; and

temporarily storing said received write requests for database data and status information and transferring said received write requests to said sub storage system by an asynchronous remote copy process.

2. A disaster recovery method according to claim 1, further comprising the steps of:

receiving a write request for said log information, database data or status information from said main storage system;

updating log information, database data and status information in said sub storage system in accordance with the contents of said received write request; and

reading log information from a position designated by the status information updated in said sub storage system at the time of start of the database process in the standby database management system and updating data in a database region on said sub storage system in accordance with the contents of said log information to thereby recover said database region on said sub storage system to a state of the database region on said main storage system.

3. A disaster recovery method according to claim 2, further comprising the step of transferring the write request for database data and status information at the time of a checkpoint together with said temporarily stored write request to said sub storage system when the write request for database data and status information is received, and then sending a notice of completion to said host computer.

4. A disaster recovery method for continuing a database process by changing an active database management system over to a standby database management system at the time of occurrence of a disaster, comprising the steps of:

receiving write requests from a main storage system of the active database management system to write log information indicating the contents of a database process executed for a database buffer of a host computer, database data updated on said database buffer and status information indicating the position of log information used for disaster recovery;

updating log information, database data and status information in a sub storage system in accordance with the contents of said received write requests; and

reading log information from a position designated by the status information at the time of start of the database process in the standby database management system and updating data in a database region on said sub storage system in accordance with the contents of said log information to thereby recover said database region on said sub storage system to a state of the database region on said main storage system.

5. A system comprising:

a first computer system including a first computer, and a first storage system connected to said first computer; and

a second storage system connected to said first storage system,

wherein said first computer sends write requests to said first storage system to write log information indicating the contents of a database process, database data and status information indicating the position of log information used for disaster recovery, and

wherein said first storage system transfers the received write request for log information to said second storage system by a synchronous remote copy process and transfers the received write request for database data and status information to said second storage system by an asynchronous remote copy process after temporarily storing the received write request for database data and status information.

6. A system according to claim 5, wherein said first storage system transfers the write request for database data and status information at the time of a checkpoint together with said temporarily stored write request to said second storage system when the write request for database data and status information is received, and then sends a notice of completion to said first computer.

7. A system according to claim 6, wherein said second storage system reads log information from a position designated by said status information in accordance with an instruction from a second computer connected to said second storage system and updates data in a database region on said second storage system in accordance with the contents of the log information to thereby recover said database region to a state of the database region on said first storage system.

15. A storage system according to claim 7, further comprising a management computer connected to said first storage system,

wherein said first storage system collects information indicating whether data transferred to said second storage system is asserted or not, and transfers the collected information to said first computer or said management computer.

16. A storage system according to claim 15, wherein said first computer controls the data amount of said database data transferred to said first storage system on the basis of said information received from said first storage system.

17. A storage system according to claim 16, wherein said first computer receives said information from said management computer.

18. A storage system according to claim 17, wherein said management computer controls the communication band of a communication line connecting said first storage system and said second storage system to each other on the basis of said information received from said first storage system.

19. A storage system according to claim 18, wherein said first storage system has a plurality of logical disks for storing said log information so that said log information received from said first computer is stored in said plurality of logical disks sequentially.

20. A storage system according to claim 19, wherein said first computer instructs said first storage system to store new log information in said plurality of logical disks on the basis of said information received from said first storage system.

21. A storage system according to claim 15, wherein said management computer compares the amount of delay of asynchronous remote copy between said first storage system and said second storage system with a predetermined threshold and makes a predetermined operation to set the amount of delay of copy to be not larger than said threshold when the amount of delay of copy exceeds the predetermined threshold.

22. A storage system according to claim 21, wherein said predetermined operation is an operation for generating a warning.

23. A storage system according to claim 21, wherein said predetermined operation is an operation for increasing a communication path between said first and second storage systems.

8. A storage system connected to a computer and to the other storage system, comprising:

a control unit; and

a disk device,

wherein said control unit receives write requests from said computer to write log information indicating the contents of a database process, database data and status information indicating the position of log information used for disaster recovery, transfers the received write request for log information to the other storage system by a synchronous remote copy process and transfers the received write request for database data and status information to the other storage system by an asynchronous remote copy process after temporarily storing the received write request.

9. A storage system according to claim 8, wherein said control unit writes the write request for database data and status information at the time of a checkpoint together with said temporarily stored write request to the other storage system when the write request for database data and status information is received, and then sends a notice of completion to said computer.

10. A storage system according to claim 9, wherein said database data and said status information are stored in different logical disks respectively but said different logical disks form one consistency group.

11. A storage system according to claim 10, wherein a plurality of logical disks for storing said log information are provided so that said log information received from said computer is stored in said plurality of logical disks sequentially.

12. A storage system according to claim 11, wherein log information newly received from said computer is written in a logical disk containing only log information reflected on one of said plurality of logical disks in which said database data are stored.

13. A storage system according to claim 12, wherein before said newly received log information is written in said logical disk, said log information stored in said logical disk is stored in another recording medium.

14. A storage system according to claim 13, wherein information indicating whether data transferred to the other storage system is asserted or not, is collected so that the collected information is transferred to said computer or to a management computer connected to said storage system.

24. A data transfer method for continuing a database process by changing an active database management system inclusive of a host computer over to a standby database management system, comprising the steps of:

receiving write requests from said host computer to write log information indicating the contents of said database process executed for a database buffer of said host computer, database data updated on said database buffer and status information indicating the position of log information used at the time of restart of the database process in said active database management system;

updating log information, database data and status information in a main storage system of said active database management system in accordance with the contents of said received write request;

transferring said received write request for log information to a sub storage system of said active database management system by a synchronous remote copy process; and

transferring said received write request for database data or status information to said sub storage system by an asynchronous remote copy process after temporarily storing said received write request for database data or status information.