Computerized system and method for data backup

• US 5,435,004 A
• Filed: 07/21/1994
• Issued: 07/18/1995
• Est. Priority Date: 07/21/1994
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Mott, James M., Cox, James O.
• Primary Examiner(s): Canney, Vincent P.
• Application Number:
  US08/278,196
• Time in Patent Office: 362 Days
• Field of Search: 395/575, 395/425, 364/268, 364/268.5, 364/285.1, 364/285, 371/10.1, 371/10.2
• US Class Current: 1/1
• CPC Class Codes: G06F 11/1466 to make the backup process non-disruptive
• CPC Class Codes: G06F 2201/80 Database-specific techniques
• CPC Class Codes: Y10S 707/99956 File allocation

Abstract

A computerized data backup system and method for dynamically preserving a consistent state of primary data stored in a logical volume of a disk volume management system during processing thereof in a real-time environment. A file system command invokes a cloning of the logical volume, thereby reserving a portion for shadow-paged blocks. A read/write translation map is generated, mapping non-shadowed pages to corresponding shadowed pages in the reserved portion. Upon generating a read command for a page in the logical volume, a map search detects that a shadow page is allocated in the shadow-paged blocks corresponding to the page and effects the read. In like manner, in response to a write command to a page of the logical volume, the map is searched and a shadow page in the shadow-paged blocks is allocated if there has been no prior allocation, whereupon writing to such allocated page occurs. The backup occurs during runtime, facilitating reading from the non-shadow paged blocks during backup.

Claims

1. A computerized method for dynamically preserving a consistent state of primary data in a logical volume of a disk volume management system during runtime, comprising

generating a file system command to clone said logical volume;

reserving a portion of said logical volume for shadow-paged blocks in response to said file system command;

generating a read/write translation map;

generating a read command of a first page of said logical volume;

detecting, in response to said read command, from a search of said map, whether a shadow page is allocated in said shadow-paged blocks corresponding to said first page; and

reading said shadow page in response to said detecting that said shadow page corresponding to said first page is allocated.

2. The method of claim 1 further including

generating a write command to a second page of said logical volume;

and

detecting, in response to said write command, from a search of said map, whether a shadow page is allocated in said shadow-paged blocks corresponding to said second page.

3. The method of claim 2 further including

allocating said shadow page in response to said detecting that said shadow page corresponding to said second page is not allocated.

4. The method of claim 2 further including

writing to said second page in response to detecting that said shadow page is allocated.

5. The method of claim 4 wherein said logical volume includes a portion of non-shadow paged blocks;

and wherein said method further includes

storing, in said map and in response to said writing, a correlation between at least one of said shadow-paged blocks and said non-shadow paged blocks.

6. The method of claim 5 wherein said at least one of said shadow-paged blocks includes said second page.

7. The method of claim 1 wherein said detecting and reading steps are performed during said runtime of said system.

8. The method of claim 4 wherein said writing step is during said runtime of said system.

9. The method of claim 5 further including

reading from said portion of said non-shadow paged blocks while said portion of said logical volume is reserved for said shadow-paged blocks.

10. The method of claim 9 further including

generating a log of said primary data;

and

prior to said detecting whether said shadow page is allocated corresponding to said first or said second page,

committing said data to said disk; and

running out said log.

11. Apparatus for dynamically preserving a consistent state of primary data in a logical volume of a disk volume management system during runtime, comprising

means for generating a file system command to clone said logical volume;

means for reserving a portion of said logical volume for shadow-paged blocks in response to said file system command;

means for generating a read/write translation map;

means for generating a read command of a first page of said logical volume;

means for detecting, in response to said read command, from a search of said map, whether a shadow page is allocated in said shadow-paged blocks corresponding to said first page; and

means for reading said shadow page in response to said detecting that said shadow page corresponding to said first page is allocated.

12. The apparatus of claim 11 further including

means for generating a write command to a second page of said logical volume;

and

means for detecting, in response to said write command, from a search of said map, whether a shadow page is allocated in said shadow-paged blocks corresponding to said second page.

13. The apparatus of claim 12 further including

means for allocating said shadow page in response to said detecting that said shadow page corresponding to said second page is not allocated.

14. The apparatus of claim 12 further including

means for writing to said second page in response to detecting that said shadow page is allocated.

15. The apparatus of claim 14 wherein said logical volume includes a portion of non-shadow paged blocks;

and wherein said apparatus further includes

means for storing, in said map and in response to said writing, a correlation between at least one of said shadow-paged blocks and said non-shadow paged blocks.

16. The apparatus claim 15 wherein said at least one of said shadow-paged blocks includes said second page.

17. The apparatus of claim 11 wherein said means for correlating includes

shadow map means for indicating used or unused states of said shadow-paged blocks.

18. The apparatus of claim 17 wherein said means for correlating further includes

primary disk map means for indicating whether said non-shadow paged blocks are shadow-paged.

19. The apparatus of claim 15 further including

means for reading from said portion of said non-shadow paged blocks while said portion of said logical volume is reserved for said shadow-paged blocks.

20. The apparatus of claim 19 further including

means for generating a log of said primary data;

and

means for committing said data to said disk prior to said detecting whether said shadow page is allocated corresponding to said first or said second page.