Enhancing performance of data storage in a dispersed storage network

• US 10,091,298 B2
• Filed: 05/27/2016
• Issued: 10/02/2018
• Est. Priority Date: 05/27/2016
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Baptist, Andrew D., Dhuse, Greg R., Khadiwala, Ravi V.
• Primary Examiner(s): Luu, Le H
• Application Number:
  US15/166,854
• Publication Number:
  US 20170346898A1
• Time in Patent Office: 858 Days
• CPC Class Codes: G06F 11/08 Error detection or correction by redundancy in data representation, e.g. by using checking codes
• CPC Class Codes: G06F 11/106 Correcting systematically all correctable errors, i.e. scrubbing
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• CPC Class Codes: G06F 16/217 Database tuning G06F16/2282 takes precedence; database performance monitoring G06F11/3409
• CPC Class Codes: G06F 16/2379 Updates performed during online database operations; commit processing
• CPC Class Codes: G06F 16/2471 Distributed queries
• CPC Class Codes: G06F 16/27 Replication, distribution or synchronisation of data between databases or within a distributed database system; Distributed database system architectures therefor
• CPC Class Codes: G06F 3/0605 by facilitating the interaction with a user or administrator
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/0635 by changing the path, e.g. traffic rerouting, path reconfiguration
• CPC Class Codes: G06F 3/064 Management of blocks
• CPC Class Codes: G06F 3/0644 Management of space entities, e.g. partitions, extents, pools
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]
• CPC Class Codes: H04L 67/1097 for distributed storage of data in networks, e.g. transport arrangements for network file system [NFS], storage area networks [SAN] or network attached storage [NAS]

Abstract

A method includes determining a level of confidence regarding a revision level for a set of encoded data slices. The method further includes, when the level of confidence is equal to or above a confidence threshold, sending write and commit requests, wherein a write and commit request includes an encoded data slice, a current revision value, and a new revision value. The method further includes, when favorable responses have been received, issuing finalize write requests. The method further includes, when the level of confidence is below the confidence threshold, sending write requests, wherein a write request includes the encoded data slice of the set of encoded data slices and a new revision value. The method further includes, when favorable write responses have been received, issuing write commit requests. The method further includes, when favorable write commit responses have been received, issuing finalize write requests.

Claims

1. A method for execution by a computing device of a dispersed storage network (DSN), the method comprises:

for a set of encoded data slices to be stored in storage units of the DSN, determining a level of confidence regarding a revision level for the set of encoded data slices;

when the level of confidence is equal to or above a confidence threshold;

sending a set of write and commit requests to the storage units of the DSN, wherein a write and commit request of the set of write and commit requests includes an encoded data slice of the set of encoded data slices, a current revision value, and a new revision value; and

when a threshold number of favorable write and commit responses have been received from the storage units in a predetermined time period, issuing a set of finalize write requests; and

when the level of confidence is below the confidence threshold;

sending a set of write requests to the storage units of the DSN, wherein a write request of the set of write requests includes the encoded data slice of the set of encoded data slices and the new revision value;

when a threshold number of favorable write responses have been received from the storage units in the predetermined time period, issuing a set of write commit requests; and

when a threshold number of favorable write commit responses have been received from the storage units in the predetermined time period, issuing the set of finalize write requests.

2. The method of claim 1 further comprises:

prior to sending the set of write requests;

sending a set of check list requests regarding the set of encoded data slices to the storage units, wherein a check list request of the set of check list requests includes a request for a current revision value for one of the set of encoded data slices stored by one of the storage units; and

determining the new revision value based on check list responses from at least some of the storage units.

3. The method of claim 1, wherein the confidence threshold comprises:

a level of certainty regarding the current revision value and the new revision value; and

a level of certainty regarding writing priority for the set of encoded data slices.

4. The method of claim 3, wherein the level of certainty regarding writing priority comprises one or more of:

information indicating that the computing device has a high probability to be an only device writing the set of encoded data slices; and

information indicating that the computing device has a highest priority with respect to writing the set of encoded data slices.

5. The method of claim 1 further comprises:

when the threshold number of favorable write and commit responses have not been received from the storage units in the predetermined time period, issuing a set of undo commands to the storage units.

6. The method of claim 1 further comprises:

when the threshold number of favorable write responses have not been received from the storage units in the predetermined time period, issuing a set of write rollback commands; and

when the threshold number of favorable write commit responses have not been received from the storage units in the predetermined time period, issuing a set of undo commands.

7. A method for execution by a storage unit of a dispersed storage network (DSN), the method comprises:

receiving a request to store an encoded data slice of a set of encoded data slices;

determining whether the request is a write and commit request or a write request;

when the request is the write and commit request;

comparing a current revision value of the write and commit request with a local current revision value associated with the encoded data slice; and

when the current revision value of the write and commit request is substantially equal to the local current revision value;

storing the encoded data slice in accordance with a new revision value of the write and commit request;

making the encoded data slice available for accessing; and

sending a favorable write and commit response; and

when the request is the write request;

determining whether a revision value of the write request corresponds to a local revision value associated with the encoded data slice;

when the revision value of the write request corresponds to the local revision value;

storing the encoded data slice;

making the encoded data slice unavailable for accessing; and

sending a favorable write response.

8. The method of claim 7, wherein the determining whether the request is the write and commit request or the write request comprises:

determining that the request is the write and commit request when the request includes both the current revision value and the new revision value; and

determining that the request is the write request when the request includes the revision value.

9. The method of claim 7 further comprises:

when the current revision value of the write and commit request is not substantially equal to the local current revision value, sending an unfavorable write and commit message.

10. The method of claim 7 further comprises:

in response to the favorable write response, receiving a commit command regarding the encoded data slice; and

in response to the commit command;

making the encoded data slice available for accessing; and

sending a favorable commit response.

11. The method of claim 7 further comprises:

in response to the favorable write and commit response, receiving an undo command; and

in response to the undo command, deleting the encoded data slice.

12. A computing device comprises:

an interface;

memory; and

a processing module operably coupled to the interface and the memory, wherein the processing module is operable to;

for a set of encoded data slices to be stored in storage units of a dispersed storage network (DSN), determine a level of confidence regarding a revision level for the set of encoded data slices;

when the level of confidence is equal to or above a confidence threshold;

send, via the interface, a set of write and commit requests to the storage units of the DSN, wherein a write and commit request of the set of write and commit requests includes an encoded data slice of the set of encoded data slices, a current revision value, and a new revision value; and

when a threshold number of favorable write and commit responses have been received from the storage units in a predetermined time period, issue, via the interface, a set of finalize write requests; and

when the level of confidence is below the confidence threshold;

send, via the interface, a set of write requests to the storage units of the DSN, wherein a write request of the set of write requests includes the encoded data slice of the set of encoded data slices and the new revision value;

when a threshold number of favorable write responses have been received from the storage units in the predetermined time period, issue, via the interface, a set of write commit requests; and

when a threshold number of favorable write commit responses have been received from the storage units in the predetermined time period, issue, via the interface, the set of finalize write requests.

13. The computing device of claim 12, wherein the processing module is further operable to:

prior to sending the set of write requests;

send, via the interface, a set of check list requests regarding the set of encoded data slices to the storage units, wherein a check list request of the set of check list requests includes a request for a current revision value for one of the set of encoded data slices stored by one of the storage units; and

determine the new revision value based on check list responses from at least some of the storage units.

14. The computing device of claim 12, wherein the confidence threshold comprises:

a level of certainty regarding the current revision value and the new revision value; and

a level of certainty regarding writing priority for the set of encoded data slices.

15. The computing device of claim 14, wherein the level of certainty regarding writing priority comprises one or more of:

information indicating that the computing device has a high probability to be an only device writing the set of encoded data slices; and

information indicating that the computing device has a highest priority with respect to writing the set of encoded data slices.

16. The computing device of claim 12, wherein the processing module is further operable to:

when the threshold number of favorable write and commit responses have not been received from the storage units in the predetermined time period, issue, via the interface, a set of undo commands to the storage units.

17. The computing device of claim 12, wherein the processing module is further operable to:

when the threshold number of favorable write responses have not been received from the storage units in the predetermined time period, issue, via the interface, a set of write rollback commands; and

when the threshold number of favorable write commit responses have not been received from the storage units in the predetermined time period, issue, via the interface, a set of undo commands.

18. A storage unit comprises:

an interface;

memory; and

a processing module operably coupled to the interface and the memory, wherein the processing module is operable to;

receive, via the interface, a request to store an encoded data slice of a set of encoded data slices;

determine whether the request is a write and commit request or a write request;

when the request is the write and commit request;

compare a current revision value of the write and commit request with a local current revision value associated with the encoded data slice; and

when the current revision value of the write and commit request is substantially equal to the local current revision value;

store the encoded data slices in the memory in accordance with a new revision value of the write and commit request;

make the encoded data slice available for accessing; and

send, via the interface, a favorable write and commit response; and

when the request is the write request;

determine whether a revision value of the write request corresponds to a local revision value associated with the encoded data slice;

when the revision value of the write request corresponds to the local revision value;

store the encoded data slice in the memory;

make the encoded data slice unavailable for accessing; and

send, via the interface, a favorable write response.

19. The storage unit of claim 18, wherein the processing module is further operable to determine whether the request is the write and commit request or the write request by:

determining that the request is the write and commit request when the request includes both the current revision value and the new revision value; and

determining that the request is the write request when the request includes the revision value.

20. The storage unit of claim 18, wherein the processing module is further operable to:

when the current revision value of the write and commit request is not substantially equal to the local current revision value, send, via the interface, an unfavorable write and commit message.

21. The storage unit of claim 18, wherein the processing module is further operable to:

in response to the favorable write response, receiving a commit command regarding the encoded data slice; and

in response to the commit command;

make the encoded data slice available for accessing; and

send, via the interface, a favorable commit response.

22. The storage unit of claim 18, wherein the processing module is further operable to:

in response to the favorable write and commit response, receive, via the interface, an undo command; and

in response to the undo command, delete the encoded data slice.