Updating an encoded data slice

1. A method comprising:

distributing, by a distributed storage (DS) processing unit, an initial set of encoded data slices for storage in a plurality of DS units, the initial set of encoded data slices including initial encoded data slices and initial parity slices, wherein initial data used to generate the initial set of encoded data slices can be reconstructed using fewer than all encoded data slices included in the initial set of encoded data slices;

receiving updated data reflecting changes to the initial data;

generating an updated encoded data slice from the updated data, the updated encoded data slice generated using an encoding function;

storing the updated encoded data slice in a first DS unit;

generating delta parity information based on the updated data, the initial data, and the encoding function;

generating updated parity slices by performing an additive operation, within a finite field, using the delta parity information and the initial parity slices; and

storing the updated parity slices in at least a second DS unit.

2. The method of claim 1 , further comprising:

transmitting an update-slice request from the DS processing unit to the first DS unit, the update-slice request including the delta parity information.

3. The method of claim 1 , wherein:

generating the delta parity information includes generating rebuilt partial parity slices.

4. The method of claim 1 , further comprising:

transmitting a message, from the DS processing unit, directing the second DS unit to store an updated parity slice, the message including information directing the second DS unit to generate the updated parity slice.

5. The method of claim 1 , wherein:

the first DS unit transmits the delta parity information to at least one of the DS processing unit and the second DS unit.

6. The method of claim 1 , wherein performing an additive operation within a finite field includes:

performing an exclusive OR (XOR) operation.

7. The method of claim 1 , wherein:

generating the delta parity information is performed using an encoding matrix associated with a systematic erasure code.

8. A distributed storage network (DSN) comprising:

a distributed storage (DS) processing unit coupled via a network to a plurality of DS units configured to store encoded data slices;

the DS processing unit including a processor and associated memory, and configured to:

distribute an initial set of encoded data slices for storage in a plurality of DS units, the initial set of encoded data slices including initial encoded data slices and initial parity slices, wherein initial data used to generate the initial set of encoded data slices can be reconstructed using fewer than all encoded data slices included in the initial set of encoded data slices;

receive updated data reflecting changes to the initial data;

generate an updated encoded data slice from the updated data, the updated encoded data slice generated using an encoding function, and reflecting changes to an initial encoded data slice stored in a first DS unit;

transmit the updated encoded data slice to the first DS unit;

the first DS unit configured to:

store the updated encoded data slice;

transmit delta parity information to at least one of the DS processing unit or a second DS unit; and

the DS processing unit further configured to:

transmit, to the second DS unit, a message directing the second DS unit to store an updated parity slice, the updated parity slice generated by performing an additive operation, within a finite field, using the delta parity information and an initial parity slice stored in the second DS unit.

9. The distributed storage network (DSN) of claim 8 , wherein the first DS unit is further configure to:

generate the delta parity information.

10. The distributed storage network (DSN) of claim 8 , wherein the DS processing unit is further configure to:

generate the delta parity information; and

transmit the delta parity information to at least one of the first DS unit and the second DS unit.

11. The distributed storage network (DSN) of claim 8 , wherein:

the delta parity information is generated based on rebuilt-partial parity slices.

12. The distributed storage network (DSN) of claim 8 , wherein the message directing the second DS unit to store the updated parity slice includes:

information directing the second DS unit to generate the updated parity slice by performing an additive operation, within a finite field, using the delta parity information and the initial parity slice.

13. The distributed storage network (DSN) of claim 8 , wherein:

the delta parity information is generated using an encoding matrix associated with a systematic erasure code.

14. The distributed storage network (DSN) of claim 8 , wherein performing an additive operation within a finite field includes:

performing an exclusive OR (XOR) operation.

15. A distributed storage (DS) processing unit comprising:

a computing core;

memory coupled to the computing core;

a network interface configured to couple the computing core to a plurality of DS units;

the DS processing unit configured to:

generate an initial set of encoded data slices for storage in a plurality of DS units, the initial set of encoded data slices including initial encoded data slices and initial parity slices, wherein initial data used to generate the initial set of encoded data slices can be reconstructed using fewer than all encoded data slices included in the initial set of encoded data slices;

transmit an initial encoded data slice to a first DS unit for storage;

transmit an initial parity slice to a second DS unit for storage, wherein the initial parity slice is associated with the initial encoded data slice;

receive updated data reflecting changes to the initial data;

generate an updated encoded data slice from the updated data, the updated encoded data slice generated using an encoding function;

transmit the updated encoded data slice in a first DS unit for storage;

obtain delta parity information generated from the updated data, the initial data, and the encoding function; and

transmit, to the second DS unit, a message directing the second DS unit to store an updated parity slice, the updated parity slice generated by performing an additive operation, within a finite field, using the delta parity information and the initial parity slice.

16. The distributed storage (DS) processing unit of claim 15 , further configured to:

obtain the delta parity information by generating the delta parity information.

17. The distributed storage (DS) processing unit of claim 15 , further configured to:

obtain the delta parity information from the first DS unit.

18. The distributed storage (DS) processing unit of claim 15 , wherein:

the delta parity information is generated based on rebuilt-partial parity slices.

19. The distributed storage (DS) processing unit of claim 15 , wherein the message directing the second DS unit to store the updated parity slice includes:

information directing the second DS unit to generate the updated parity slice by performing an additive operation, within a finite field, using the delta parity information and the initial parity slice.

20. The distributed storage (DS) processing unit of claim 15 , wherein:

the delta parity information is generated using an encoding matrix associated with a systematic erasure code; and

performing an additive operation within a finite field includes performing an exclusive OR (XOR) operation.