REBUILDING A DATA REVISION IN A DISPERSED STORAGE NETWORK

• US 20150212887A1
• Filed: 04/06/2015
• Published: 07/30/2015
• Est. Priority Date: 07/30/2009
• Status: Active Grant

• Current Assignee: Pure Storage, Inc.
• Original Assignee: Cleversafe Incorporated (International Business Machines Corporation)
• Inventors: Dhuse, Greg, Volvovski, Ilya, Mark, Zachary J., Vas, Sebastien, Baptist, Andrew
• Granted Patent: US 9,563,507 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• CPC Class Codes: G06F 11/1092 Rebuilding, e.g. when physically replacing a failing disk
• CPC Class Codes: G06F 2211/1028 Distributed, i.e. distributed RAID systems with parity
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/0647 Migration mechanisms
• CPC Class Codes: G06F 3/0689 Disk arrays, e.g. RAID, JBOD
• CPC Class Codes: H04L 2209/04 Masking or blinding
• CPC Class Codes: H04L 2209/34 Encoding or coding, e.g. Huffman coding or error correction
• CPC Class Codes: H04L 9/085 Secret sharing or secret splitting, e.g. threshold schemes
• CPC Class Codes: H04L 9/0863 involving passwords or one-time passwords network architectures or network communication protocols for using one-time keys in a packet data network H04L63/067
• CPC Class Codes: H04L 9/0869 involving random numbers or seeds
• CPC Class Codes: H04L 9/0894 Escrow, recovery or storing of secret information, e.g. secret key escrow or cryptographic key storage

Abstract

A method begins by a processing module storing a set of encoded data slices in storage units. A data segment of data is encoded, in accordance with dispersed storage error encoding parameters, to produce the set of encoded data slices. The dispersed storage error encoding parameters include a decode threshold number and a pillar width number, which is at least twice the decode threshold number. The method continues with the processing module processing a first request for retrieval of the data segment by retrieving a first sub-set of encoded data slices, which includes the decode threshold number, and decoding them to produce a first recovered data segment. The method continues with the processing module processing a second request for retrieval of the data segment by retrieving a second sub-set of encoded data slices, which includes the decode threshold number, and decoding them to produce a second recovered data segment.

Claims

1. A method for execution by a processing module of a computing device, the method comprises the steps of:

storing a set of encoded data slices in storage units of a dispersed storage network, wherein a data segment of data is encoded, in accordance with dispersed storage error encoding parameters, to produce the set of encoded data slices, wherein the dispersed storage error encoding parameters include a pillar width number that represents a total number of encoded data slices in the set of encoded data slices and a decode threshold number with represents a minimum number of encoded data slices that is needed to recover the data segment, and wherein the pillar width number is at least twice the decode threshold number;

processing a first request for retrieval of the data segment by;

retrieving a first sub-set of encoded data slices of the set of encoded data slices, wherein the first sub-set of encoded data slices includes the decode threshold number of encoded data slices;

decoding the first sub-set of encoded data slices to produce a first recovered data segment; and

processing a second request for retrieval of the data segment by;

retrieving a second sub-set of encoded data slices of the set of encoded data slices, wherein the second sub-set of encoded data slices includes the decode threshold number of encoded data slices;

decoding the second sub-set of encoded data slices to produce a second recovered data segment.

2. The method of claim 1 further comprises:

determining that the first sub-set of encoded data slices and the second sub-set of encoded data slices have different revision levels; and

determining a remedy for the difference in revision levels.

3. The method of claim 2, wherein the remedy comprises one or more of:

rebuilding the first or the second sub-set of encoded data slices;

maintaining the first and second sub-set of encoded data slices; and

deleting the first or the second sub-set of encoded data slices.

4. The method of claim 1 further comprises:

processing a third request for retrieval of the data segment by;

retrieving a third sub-set of encoded data slices of the set of encoded data slices, wherein the third sub-set of encoded data slices includes the decode threshold number of encoded data slices;

decoding the third sub-set of encoded data slices to produce a third recovered data segment.

5. The method of claim 1 further comprises:

updating the first sub-set of encoded data slices with a more current revision level.

6. A computer comprises:

an interface;

a memory; and

a processing module operable to;

store a set of encoded data slices in storage units of a dispersed storage network, wherein a data segment of data is encoded, in accordance with dispersed storage error encoding parameters, to produce the set of encoded data slices, wherein the dispersed storage error encoding parameters include a pillar width number that represents a total number of encoded data slices in the set of encoded data slices and a decode threshold number with represents a minimum number of encoded data slices that is needed to recover the data segment, and wherein the pillar width number is at least twice the decode threshold number;

process a first request for retrieval of the data segment by;

retrieving a first sub-set of encoded data slices of the set of encoded data slices, wherein the first sub-set of encoded data slices includes the decode threshold number of encoded data slices;

decoding the first sub-set of encoded data slices to produce a first recovered data segment; and

process a second request for retrieval of the data segment by;

retrieving a second sub-set of encoded data slices of the set of encoded data slices, wherein the second sub-set of encoded data slices includes the decode threshold number of encoded data slices;

decoding the second sub-set of encoded data slices to produce a second recovered data segment.

7. The computer of claim 6, wherein the processing module is further operable to:

determine that the first sub-set of encoded data slices and the second sub-set of encoded data slices have different revision levels; and

determine a remedy for the difference in revision levels.

8. The computer of claim 7, wherein the remedy comprises one or more of:

rebuilding the first or the second sub-set of encoded data slices;

maintaining the first and second sub-set of encoded data slices; and

deleting the first or the second sub-set of encoded data slices.

9. The computer of claim 6, wherein the processing module is further operable to:

process a third request for retrieval of the data segment by;

retrieving a third sub-set of encoded data slices of the set of encoded data slices, wherein the third sub-set of encoded data slices includes the decode threshold number of encoded data slices;

decoding the third sub-set of encoded data slices to produce a third recovered data segment.

10. The computer of claim 6, wherein the processing module is further operable to:

update the first sub-set of encoded data slices with a more current revision level.

11. A non-transitory computer readable storage device comprises:

a first memory section that stores operational instructions that, when executed by a computing device, causes the computing device to;

store a set of encoded data slices in storage units of a dispersed storage network, wherein a data segment of data is encoded, in accordance with dispersed storage error encoding parameters, to produce the set of encoded data slices, wherein the dispersed storage error encoding parameters include a pillar width number that represents a total number of encoded data slices in the set of encoded data slices and a decode threshold number with represents a minimum number of encoded data slices that is needed to recover the data segment, and wherein the pillar width number is at least twice the decode threshold number; and

a second memory section that stores operational instructions that, when executed by the computing device, causes the computing device to;

process a first request for retrieval of the data segment by;

retrieving a first sub-set of encoded data slices of the set of encoded data slices, wherein the first sub-set of encoded data slices includes the decode threshold number of encoded data slices;

decoding the first sub-set of encoded data slices to produce a first recovered data segment; and

process a second request for retrieval of the data segment by;

retrieving a second sub-set of encoded data slices of the set of encoded data slices, wherein the second sub-set of encoded data slices includes the decode threshold number of encoded data slices;

decoding the second sub-set of encoded data slices to produce a second recovered data segment.

12. The non-transitory computer readable storage device of claim 11 further comprises:

a third memory section that stores operational instructions that, when executed by the computing device, causes the computing device to;

determine that the first sub-set of encoded data slices and the second sub-set of encoded data slices have different revision levels; and

determine a remedy for the difference in revision levels.

13. The non-transitory computer readable storage device of claim 12, wherein the remedy comprises one or more of:

rebuilding the first or the second sub-set of encoded data slices;

maintaining the first and second sub-set of encoded data slices; and

deleting the first or the second sub-set of encoded data slices.

14. The non-transitory computer readable storage device of claim 11, wherein the second memory section further stores operational instructions that, when executed by the computing device, causes the computing device to:

process a third request for retrieval of the data segment by;

retrieving a third sub-set of encoded data slices of the set of encoded data slices, wherein the third sub-set of encoded data slices includes the decode threshold number of encoded data slices;

decoding the third sub-set of encoded data slices to produce a third recovered data segment.

15. The non-transitory computer readable storage device of claim 11 further comprises:

a third memory section that stores operational instructions that, when executed by the computing device, causes the computing device to;

update the first sub-set of encoded data slices with a more current revision level.