Method and apparatus for rebuilding data in a dispersed data storage network

1. A method for execution by one or more computers associated with a dispersed data storage network, the method comprises:

determining that a disk drive of a slice server has been replaced with a new disk drive;

identifying a data slice that was stored on the disk drive;

identifying a data segment based on the identified data slice, wherein the data segment was encoded in accordance with an information dispersal function to produce a set of data slices, which includes the identified data slice;

identifying one or more other slice servers that are storing other data slices of the set of data slices;

retrieving, from the one or more other slice servers, a sufficient number of the other data slices to reconstruct the data segment;

decoding the sufficient number of the other data slices in accordance with the information dispersal function to reconstruct the data segment;

encoding the reconstructed data segment in accordance with the information dispersal algorithm to produce a new set of data slices; and

selecting a data slice of the new set of data slices as a rebuilt data slice of the identified data slice.

2. The method of claim 1 further comprises:

outputting the rebuilt data slice to the slice server for storage therein.

3. The method of claim 1 , wherein the identifying the data slice comprises:

ascertaining a range of data slices assigned to the disk drive;

determining whether the data slice is within the range of data slices; and

when the data slice is within the range of data slices, identifying the data slice.

4. The method of claim 1 , wherein the identifying the data segment comprises:

accessing a rebuild record to identify the data segment based on the identified data slice.

5. The method of claim 1 further comprises:

decoding the sufficient number of the other data slices by:

arranging the sufficient number of other data slices into a reconstructed coded matrix; and

decoding the reconstructed coded matrix using a decoding matrix function in accordance with the information dispersal algorithm to reconstruct the data segment; and

encoding the reconstructed data segment by:

arranging the reconstructed data segment into the data matrix;

encoding the data matrix using an encoding matrix function in accordance with the information dispersal algorithm to produce a coded matrix; and

arranging the coded matrix into the new set of data slices.

6. A method for execution by one or more computers associated with a dispersed data storage network, the method comprises:

determining whether a data slice stored by a slice server is outdated, is corrupt, is missing, or has a checksum error;

when the data slice is outdated, is corrupt, is missing, or has a checksum error, identifying a data segment based on the data slice, wherein the data segment was encoded in accordance with an information dispersal function to produce a set of data slices, which includes the identified data slice;

identifying one or more other slice servers that are storing other data slices of the set of data slices;

retrieving, from the one or more other slice servers, a sufficient number of the other data slices to reconstruct the data segment;

decoding the sufficient number of the other data slices in accordance with the information dispersal function to reconstruct the data segment;

encoding the reconstructed data segment in accordance with the information dispersal algorithm to produce a new set of data slices; and

selecting a data slice of the new set of data slices as a rebuilt data slice of the data slice.

7. The method of claim 6 , wherein determining that the data slice is outdated comprises:

determining a transaction identifier associated with the data slice;

determining whether the transaction identifier corresponds to a current transaction regarding the data segment based on transaction identifiers of at least some of the other data slices; and

when the transaction identifier does not correspond to the current transaction regarding the data segment, indicating that the data slice is outdated.

8. The method of claim 6 , wherein the determining that the data slice has the checksum error comprises:

receiving the data slice, wherein the data slice includes an appended checksum;

calculating a checksum for the received data slice;

comparing the calculated checksum with the appended checksum; and

when the calculated checksum does not match the appended checksum, indicating that the data slice has the checksum error.

9. The method of claim 6 , wherein the identifying the data segment comprises:

accessing a rebuild record to identify the data segment based on the identified data slice.

10. The method of claim 6 further comprises:

decoding the sufficient number of the other data slices by:

arranging the sufficient number of other data slices into a reconstructed coded matrix; and

decoding the reconstructed coded matrix using a decoding matrix function in accordance with the information dispersal algorithm to reconstruct the data segment; and

encoding the reconstructed data segment by:

arranging the reconstructed data segment into the data matrix;

encoding the data matrix using an encoding matrix function in accordance with the information dispersal algorithm to produce a coded matrix; and

arranging the coded matrix into the new set of data slices.

11. A computer for use within a dispersed data storage network, the computer comprises:

a network interface for interfacing with a network, wherein a plurality of data slice servers is operably coupled to the network; and

a central processing unit, wherein the central processing unit is operably coupled to:

determine that a disk drive of a slice server has been replaced with a new disk drive;

identify a data slice that was stored on the disk drive;

identify a data segment based on the identified data slice, wherein the data segment was encoded in accordance with an information dispersal function to produce a set of data slices, which includes the identified data slice;

identify one or more other slice servers that are storing other data slices of the set of data slices;

retrieve, from the one or more other slice servers via the network interface, a sufficient number of the other data slices to reconstruct the data segment;

decode the sufficient number of the other data slices in accordance with the information dispersal function to reconstruct the data segment;

encode the reconstructed data segment in accordance with the information dispersal algorithm to produce a new set of data slices; and

select a data slice of the new set of data slices as a rebuilt data slice of the identified data slice.

12. The computer of claim 11 , wherein the central processing unit is further operable to:

output, via the network interface, the rebuilt data slice to the slice server for storage therein.

13. The computer of claim 11 , wherein the central processing unit is further operable to identify the data slice by:

ascertaining a range of data slices assigned to the disk drive;

determining whether the data slice is within the range of data slices; and

when the data slice is within the range of data slices, identifying the data slice.

14. The computer of claim 11 , wherein the central processing unit is further operable to identify the data segment by:

accessing a rebuild record to identify the data segment based on the identified data slice.

15. The computer of claim 11 , wherein the central processing unit is further operable to:

decode the sufficient number of the other data slices by:

arranging the sufficient number of other data slices into a reconstructed coded matrix; and

decoding the reconstructed coded matrix using a decoding matrix function in accordance with the information dispersal algorithm to reconstruct the data segment; and

encode the reconstructed data segment by:

arranging the reconstructed data segment into the data matrix;

encoding the data matrix using an encoding matrix function in accordance with the information dispersal algorithm to produce a coded matrix; and

arranging the coded matrix into the new set of data slices.

16. A computer for use within a dispersed data storage network, the computer comprises:

a network interface for interfacing with a network, wherein a plurality of data slice servers is operably coupled to the network; and

a central processing unit, wherein the central processing unit is operably coupled to:

determine whether a data slice stored by a slice server is outdated, is corrupt, is missing, or has a checksum error;

when the data slice is outdated, is corrupt, is missing, or has a checksum error, identify a data segment based on the data slice, wherein the data segment was encoded in accordance with an information dispersal function to produce a set of data slices, which includes the identified data slice;

identify one or more other slice servers that are storing other data slices of the set of data slices;

retrieve, from the one or more other slice servers via the network interface, a sufficient number of the other data slices to reconstruct the data segment;

decode the sufficient number of the other data slices in accordance with the information dispersal function to reconstruct the data segment;

encode the reconstructed data segment in accordance with the information dispersal algorithm to produce a new set of data slices; and

select a data slice of the new set of data slices as a rebuilt data slice of the data slice.

17. The computer of claim 16 , wherein the central processing unit is further operable to determine that the data slice is outdated by:

determining a transaction identifier associated with the data slice;

determining whether the transaction identifier corresponds to a current transaction regarding the data segment based on transaction identifiers of at least some of the other data slices; and

when the transaction identifier does not correspond to the current transaction regarding the data segment, indicating that the data slice is outdated.

18. The computer of claim 16 , wherein the central processing unit is further operable to determine that the data slice has the checksum error by:

receiving the data slice, wherein the data slice includes an appended checksum;

calculating a checksum for the received data slice;

comparing the calculated checksum with the appended checksum; and

when the calculated checksum does not match the appended checksum, indicating that the data slice has the checksum error.

19. The computer of claim 16 , wherein the central processing unit is further operable to identify the data segment by:

accessing a rebuild record to identify the data segment based on the identified data slice.

20. The computer of claim 16 , wherein the central processing unit is further operable to:

decode the sufficient number of the other data slices by:

arranging the sufficient number of other data slices into a reconstructed coded matrix; and

decoding the reconstructed coded matrix using a decoding matrix function in accordance with the information dispersal algorithm to reconstruct the data segment; and

encode the reconstructed data segment by:

arranging the reconstructed data segment into the data matrix;

encoding the data matrix using an encoding matrix function in accordance with the information dispersal algorithm to produce a coded matrix; and

arranging the coded matrix into the new set of data slices.