Method and system using checksums to repair data
View Patent ↗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.
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.