Method and system using checksums to repair data

• US 7,689,877 B2
• Filed: 04/19/2006
• Issued: 03/30/2010
• Est. Priority Date: 11/04/2005
• Status: Active Grant

• Current Assignee: Oracle America, Inc. (Oracle Corporation)
• Original Assignee: Sun Microsystems Incorporated (Oracle Corporation)
• Inventors: Bonwick, Jeffrey S., Moore, William H.
• Primary Examiner(s): Ellis; Kevin L
• Assistant Examiner(s): GANDHI, DIPAKKUMAR B
• Application Number:
  US11/406,756
• Publication Number:
  US 20070106925A1
• Time in Patent Office: 1,441 Days
• Field of Search: None
• US Class Current: 714/710
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• CPC Class Codes: G06F 11/1088 Reconstruction on already foreseen single or plurality of spare disks

Abstract

A method for reconstructing corrupted data, which includes determining a number of non-parity disks (n), selecting a first combination of n-1 non-parity disks, obtaining a first set of physical blocks from the first combination of n-1 non-parity disks, obtaining a parity block associated with the first set of physical blocks, reconstructing a first physical block using the first set of physical blocks and the parity block, combining the first physical block and the first set of physical blocks to obtain a first reconstructed logical block, checksuming the first reconstructed logical block to obtain a first calculated checksum, and determining whether the first calculated checksum is equal to a stored checksum associated with the first reconstructed logical block.

Claims

1. A computer readable medium with software instructions stored thereon to:

determine a number of non-parity disks (n);

select a first combination of n-1 non-parity disks;

obtain a first set of physical blocks from the first combination of n-1 non-parity disks;

obtain a parity block associated with the first set of physical blocks;

reconstruct a first physical block using the first set of physical blocks and the parity block;

combine the first physical block and the first set of physical blocks to obtain a first reconstructed logical block;

checksum the first reconstructed logical block to obtain a first calculated checksum; and

determine whether the first calculated checksum is equal to a stored checksum associated with the first reconstructed logical block.

2. The computer readable medium of claim 1, further comprising software instructions to:

replace a corresponding physical block in a storage pool with the first physical block, if the first calculated checksum is equal to the stored checksum associated with the logical block.

3. The computer readable medium of claim 1, further comprising software instructions to:

if the first calculated checksum is not equal to the stored checksum associated with the logical block;

select a second combination of n-1 non-parity disks;

obtain a second set of physical blocks from the second combination of n-1 non- parity disks;

reconstruct a second physical block using the second set of physical blocks and the parity block;

combine the second physical block and the second set of physical blocks to obtain a second reconstructed logical block;

checksum the second reconstructed logical block to obtain a second calculated checksum; and

determine whether the second calculated checksum is equal to a stored checksum associated with the second reconstructed logical block.

4. The computer readable medium of claim 1, wherein the stored checksum is stored in a block pointer referencing the logical block.

5. The computer readable medium of claim 1, wherein the logical block is stored using a RAID scheme.

6. The computer readable medium of claim 1, wherein the logical block is a data block.

7. The computer readable medium of claim 1, wherein the logical block is an indirect block.

8. The computer readable medium of claim 1, wherein the logical block is associated with a file.

9. A system, comprising:

a processor; and

a computer usable storage medium having computer readable program code embodied therein, the computer readable program code adapted to, when executed by the processor, implements a method, the method comprising;

determining a number of non-parity disks (n);

selecting a first combination of n-1 non-parity disks;

obtaining a first set of physical blocks from the first combination of n-1 non-parity disks;

obtaining a parity block associated with the first set of physical blocks;

reconstructing a first physical block using the first set of physical blocks and the parity block;

combining the first physical block and the first set of physical blocks to obtain a first reconstructed logical block;

checksuming the first reconstructed logical block to obtain a first calculated checksum; and

determining whether the first calculated checksum is equal to a stored checksum associated with the first reconstructed logical block.

10. The system of claim 9, the method further comprising:

replacing a corresponding physical block in a storage pool with the first physical block, if the first calculated checksum is equal to the stored checksum associated with the logical block.

11. The system of claim 9, the method further comprising:

if the first calculated checksum is not equal to the stored checksum associated with the logical block;

selecting a second combination of n-1 non-parity disks;

obtaining a second set of physical blocks from the second combination of n-1 non-parity disks;

reconstructing a second physical block using the second set of physical blocks and the parity block;

combining the second physical block and the second set of physical blocks to obtain a second reconstructed logical block;

checksuming the second reconstructed logical block to obtain a second calculated checksum; and

determining whether the second calculated checksum is equal to a stored checksum associated with the second reconstructed logical block.

12. The system of claim 9, wherein the stored checksum is stored in a block pointer referencing the logical block.

13. The system of claim 9, wherein the logical block is stored using a RAID scheme.

14. The system of claim 9, wherein the logical block is a data block.

15. The system of claim 9, wherein the logical block is an indirect block.

16. The system of claim 9, wherein the logical block is associated with a file.