REBUILDING AN ENCODED DATA SLICE WITHIN A DISPERSED STORAGE NETWORK

• US 20130238565A1
• Filed: 04/30/2013
• Published: 09/12/2013
• Est. Priority Date: 11/24/2009
• Status: Active Grant

• Current Assignee: Pure Storage, Inc.
• Original Assignee: Cleversafe Incorporated (International Business Machines Corporation)
• Inventors: Resch, Jason K., Dhuse, Greg
• Granted Patent: US 9,465,824 B2
• Time in Patent Office: Days
• US Class Current: 707/685
• CPC Class Codes: G06F 11/1402 Saving, restoring, recovering or retrying
• CPC Class Codes: G06F 16/215 Improving data quality; Data cleansing, e.g. de-duplication, removing invalid entries or correcting typographical errors
• CPC Class Codes: G06F 21/64 Protecting data integrity, e.g. using checksums, certificates or signatures
• CPC Class Codes: G06F 21/80 in storage media based on magnetic or optical technology, e.g. disks with sectors preventing unauthorised reproduction or copying of disc-type recordable media G11B20/00
• CPC Class Codes: H04L 9/085 Secret sharing or secret splitting, e.g. threshold schemes

Abstract

A method begins with a computing device of a dispersed storage network (DSN) determining that an encoded data slice of a set of encoded data slices requires rebuilding and sending partial rebuild requests to storage units of the DSN. The method continues with one of the storage units generating a partial rebuilt slice based one or more encoded data slices of the set of encoded data slices stored by the one of the storage units and securing the partial rebuilt slice using a shared secret scheme that is shared among the storage units to produce a secured partial rebuilt slice. The method continues with the computing device receiving a set of secured partial rebuilt slices from the storage units, recovering a set of partial rebuilt slices from the set of secured partial rebuilt slices, and rebuilding the encoded data slice from the set of partial rebuilt slices.

Claims

1. A method comprises:

determining, by a computing device of a dispersed storage network (DSN), that an encoded data slice of a set of encoded data slices requires rebuilding, wherein a data segment is encoded using an error coding dispersal storage function to produce the set of encoded data slices;

sending, by the computing device, partial rebuild requests to storage units of the DSN, wherein the set of encoded data slices are distributedly stored within the storage units;

generating, by one of the storage units, a partial rebuilt slice based one or more encoded data slices of the set of encoded data slices stored by the one of the storage units;

securing, by the one of the storage units, the partial rebuilt slice using a shared secret scheme that is shared among the storage units to produce a secured partial rebuilt slice;

receiving, by the computing device, a set of secured partial rebuilt slices from the storage units;

recovering, by the computing device, a set of partial rebuilt slices from the set of secured partial rebuilt slices based on the shared secret scheme; and

rebuilding, by the computing device, the encoded data slice from the set of partial rebuilt slices.

2. The method of claim 1, wherein the computing device determining that the encoded data slice requires rebuilding further comprises:

identifying the storage units from a plurality of storage units of the DSN for facilitating the rebuilding.

3. The method of claim 1, wherein the one of the storage units generating the partial rebuilt slice comprises:

obtaining an encoding matrix associated with the error coding dispersal storage function;

reducing the encoding matrix for generating the partial rebuilt slice to produce a reduced matrix;

inverting the reduced matrix to produce a partial decode matrix; and

generating the partial rebuilt slice based on the partial decode matrix and the one or more encoded data slices of the set of encoded data slices stored by the one of the storage units.

4. The method of claim 1, wherein the one of the storage units generating the partial rebuilt slice comprises:

providing a copy of the one or more encoded data slices as the partial rebuilt slice.

5. The method of claim 1, wherein the one of the storage units securing the partial rebuilt slice further comprises:

identifying a common shared secret value that is commonly shared by the storage units and the computing device; and

securing the partial rebuilt slice using the common shared secret value.

6. The method of claim 1, wherein the one of the storage units securing the partial rebuilt slice further comprises:

identifying a unique shared secret value that is commonly shared by the one of the storage units and the computing device; and

securing the partial rebuilt slice using the unique shared secret value.

7. The method of claim 1 further comprises:

generating, by the computing device, the partial rebuild requests to include identity of the storage units;

securing, by the one of the storage units, the partial rebuilt slice using shared secret values of the other storage units to produce a secured partial rebuilt slice; and

recovering, by the computing device, the set of partial rebuilt slices from the set of secured partial rebuilt slices based on the shared secret values of the storage units.

8. The method of claim 7, wherein the recovering the set of partial rebuilt slices comprises:

exclusive ORing the set of secure partial rebuilt slices with the shared secret values of the storage units, wherein the computing device received 2*n copies of each of the shared secret values, and wherein n is greater than or equal to one.

9. The method of claim 1, wherein the computing device recovers the set of partial rebuilt slices further comprises at least one of:

decrypting the set of secured partial rebuilt slices using a common shared secret value, wherein the common shared secret value that is commonly shared by the storage units and the computing device; and

performing a mathematical function on the set of secured partial rebuilt slices using the common shared secret value.

10. A dispersed storage network (DSN) comprises:

a computing device that includes a processing module and memory; and

storage units, wherein a storage unit of the storage units includes a storage processing module and storage memory, wherein;

the processing module determines that an encoded data slice of a set of encoded data slices requires rebuilding, wherein a data segment is encoded using an error coding dispersal storage function to produce the set of encoded data slices;

the processing module sends partial rebuild requests to the storage units of the DSN, wherein the set of encoded data slices are distributedly stored within the storage units;

a storage processing module of one of the storage units generates a partial rebuilt slice based on one or more encoded data slices of the set of encoded data slices stored in a storage memory of the one of the storage units;

the storage processing module secures the partial rebuilt slice using a shared secret scheme that is shared among the storage units to produce a secured partial rebuilt slice;

the processing module receives a set of secured partial rebuilt slices from the storage units;

the processing module recovers a set of partial rebuilt slices from the set of secured partial rebuilt slices based on the shared secret scheme; and

the processing module rebuilds the encoded data slice from the set of partial rebuilt slices.

11. The DSN of claim 10, wherein the processing module further determines that the encoded data slice requires rebuilding by:

identifying the storage units from a plurality of storage units of the DSN for facilitating the rebuilding.

12. The DSN of claim 10, wherein the storage processing module generates the partial rebuilt slice by:

obtaining an encoding matrix associated with the error coding dispersal storage function;

reducing the encoding matrix for generating the partial rebuilt slice to produce a reduced matrix;

inverting the reduced matrix to produce a partial decode matrix; and

generating the partial rebuilt slice based on the partial decode matrix and the one or more encoded data slices of the set of encoded data slices stored in the storage memory.

13. The DSN of claim 10, wherein the storage processing module generates the partial rebuilt slice by:

providing a copy of the one or more encoded data slices, from the storage memory, as the partial rebuilt slice.

14. The DSN of claim 10, wherein the storage processing module further secures the partial rebuilt slice by:

identifying a common shared secret value that is commonly shared by the storage units and the computing device; and

securing the partial rebuilt slice using the common shared secret value.

15. The DSN of claim 10, wherein the storage processing module further secures the partial rebuilt slice by:

identifying a unique shared secret value that is commonly shared by the one of the storage units and the computing device; and

securing the partial rebuilt slice using the unique shared secret value.

16. The DSN of claim 10 further comprises:

the processing module generates the partial rebuild requests to include identity of the storage units;

the storage processing module secures the partial rebuilt slice using shared secret values of the other storage units to produce a secured partial rebuilt slice; and

the processing module recovers the set of partial rebuilt slices from the set of secured partial rebuilt slices based on the shared secret values of the storage units.

17. The DSN of claim 16, wherein the processing module recovers the set of partial rebuilt slices by:

exclusive ORing the set of secure partial rebuilt slices with the shared secret values of the storage units, wherein the computing device received 2*n copies of each of the shared secret values, and wherein n is greater than or equal to one.

18. The DSN of claim 10, wherein the processing module further recovers the set of partial rebuilt slices by at least one of:

decrypting the set of secured partial rebuilt slices using a common shared secret value, wherein the common shared secret value that is commonly shared by the storage units and the computing device; and

performing a mathematical function on the set of secured partial rebuilt slices using the common shared secret value.