Verifying a status level of stored encoded data slices

• US 10,140,178 B2
• Filed: 04/07/2015
• Issued: 11/27/2018
• Est. Priority Date: 06/05/2014
• Status: Expired due to Fees

• Current Assignee: Pure Storage, Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Resch, Jason K., Abhijeet, Kumar
• Primary Examiner(s): Vallecillo, Kyle
• Application Number:
  US14/680,575
• Publication Number:
  US 20150355966A1
• Time in Patent Office: 1,330 Days
• CPC Class Codes: G06F 11/0709 in a distributed system consisting of a plurality of standalone computer nodes, e.g. clusters, client-server systems
• CPC Class Codes: G06F 11/0727 in a storage system, e.g. in a DASD or network based storage system drivers for digital recording or reproducing units G06F3/06; circuits for error detection or correction within digital recording or reproducing units G11B20/18; 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], H04L67/1097
• CPC Class Codes: G06F 11/0775 Content or structure details of the error report, e.g. specific table structure, specific error fields
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• CPC Class Codes: G06F 16/00 Information retrieval; Database structures therefor; File system structures therefor
• CPC Class Codes: G06F 2211/1004 Adaptive RAID, i.e. RAID system adapts to changing circumstances, e.g. RAID1 becomes RAID5 as disks fill up
• 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 3/064 Management of blocks
• 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 begins by a processing module of a dispersed storage network (DSN) retrieving a decode threshold number of encoded data slices of a set of encoded data slices from a first grouping of storage units of the DSN. The method continues with the processing module determining a first status level indication of the retrieved decode threshold number of encoded data slices and sending check status request messages to a second grouping of storage units of the DSN. The method continues with the processing module receiving check status response messages and processing the check response messages to produce a second status level indication. When the second status level indication is substantially equal to the first status level indication, the method continues with the processing module indicating that the decode threshold number of encoded data slices is of a common status level as other encoded data slices of encoded data slices.

Claims

1. A method for execution by one or more processing modules of one or more computing devices of a dispersed storage network (DSN), the method comprises:

retrieving a decode threshold number of encoded data slices of a set of encoded data slices from a first grouping of storage units of the DSN, wherein a data segment of a data object 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 includes the decode threshold number and a width number, wherein the decode threshold number corresponds to a minimum number of encoded data slices of the set of encoded data slices that are needed to recover the data segment, wherein the width number corresponds to a total number of encoded data slices in the set of encoded data slices, and wherein the decode threshold number is less than or equal to one-half of the width number; and

to verify that the decode threshold number of encoded data slices is of a common status level as other encoded data slices of the set of encoded data slices;

determining a first status level indication of the retrieved decode threshold number of encoded data slices;

sending check status request messages to a second grouping of storage units of the DSN, wherein a check status request message of the check status request messages is requesting that a storage unit of the second grouping of storage units provide a status level indication of one of the other encoded data slices stored by the storage unit, wherein the second grouping of storage units store remaining encoded data slices of the set of encoded data slices, wherein the remaining encoded data slices is the total number of encoded data slices less the decode threshold number of encoded data slices;

receiving check status response messages from the second grouping of storage units, wherein a check status response message of the check status response messages includes the status level indication of the one of the other encoded data slices;

processing the check response messages to produce a second status level indication;

when the second status level indication is greater than the first status level indication, sending a new retrieval request for the decode threshold number of encoded data slices having the second status level indication to the second grouping of storage units of the DSN; and

when the second status level indication is substantially equal to the first status level indication, indicating that the decode threshold number of encoded data slices is of the common status level as the other encoded data slices.

2. The method of claim 1, wherein the retrieving the decode threshold number of encoded data slices comprises:

receiving a first decode threshold number of encoded data slices;

determining whether each encoded data slice of the first decode threshold number of the encoded data slices have a same status level;

when each encoded data slice of the first decode threshold number of the encoded data slices have the same status level, using the first decode threshold number of encoded data slices as the decode threshold number of encoded data slices; and

when each encoded data slice of the first decode threshold number of the encoded data slices do not have the same status level,

receiving a second decode threshold number of encoded data slices; and

when each encoded data slice of the second decode threshold number of the encoded data slices have the same status level, using the second decode threshold number of encoded data slices as the decode threshold number of encoded data slices.

3. The method of claim 1 further comprises:

when the decode threshold number of encoded data slices is of the common status level as the other encoded data slices, decoding the decode threshold number of encoded data slices to recover the data segment.

4. The method of claim 1 further comprises:

when the second status level indication is less than the first status level indication, determining whether to retrieve the decode threshold number of the other encoded data slices; and

when the determination is to retrieve the decode threshold number of the other encoded data slices;

retrieving the decode threshold number of the other encoded data slices; and

decoding the decode threshold number of the other encoded data slices to recover the data segment having the second status level.

5. The method of claim 4 further comprises:

determining to retrieve the decode threshold number of the other encoded data slices based on one or more of;

data concurrency of the data object;

time concurrency of write requests of the data segment;

a request for all status levels of the data segment; and

user identifiers of the first and second status levels of the data segment.

6. The method of claim 5 further comprises:

decoding the decode threshold number of the encoded data slices to recover the data segment having the first status level; and

when the decode threshold number of the other encoded data slices was retrieved based on the time concurrency of write requests of the data segment, merging changes of the data segment having the second status level indication into the data segment having the first status level indication.

7. The method of claim 1 further comprises:

a number of encoded data slices of the other encoded data slices is substantially equal to a read check number, wherein the read check number is in a range of numbers between the decode threshold number and the width number minus the decode threshold number.

8. The method of claim 1 further comprises:

when the second status level indication is not substantially equal to the first status level indication, determining whether to maintain in the first and second groupings of storage units encoded data slices having different status level indications or to update the encoded data slices having different status level indications.

9. A non-transitory computer readable storage medium comprises:

at least one memory section that stores operational instructions that, when executed by one or more processing modules of one or more computing devices of a dispersed storage network (DSN), causes the one or more computing devices to;

retrieve a decode threshold number of encoded data slices of a set of encoded data slices from a first grouping of storage units of the DSN, wherein a data segment of a data object 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 includes the decode threshold number and a width number, wherein the decode threshold number corresponds to a minimum number of encoded data slices of the set of encoded data slices that are needed to recover the data segment, wherein the width number corresponds to a total number of encoded data slices in the set of encoded data slices, and wherein the decode threshold number is less than or equal to one-half of the width number; and

to verify that the decode threshold number of encoded data slices is of a common status level as other encoded data slices of the set of encoded data slices;

determine a first status level indication of the retrieved decode threshold number of encoded data slices;

send check status request messages to a second grouping of storage units of the DSN, wherein a check status request message of the check status request messages is requesting that a storage unit of the second grouping of storage units provide a status level indication of one of the other encoded data slices stored by the storage unit, wherein the second grouping of storage units store remaining encoded data slices of the set of encoded data slices, wherein the remaining encoded data slices is the total number of encoded data slices less the decode threshold number of encoded data slices;

receive check status response messages from the second grouping of storage units, wherein a check status response message of the check status response messages includes the status level indication of the one of the other encoded data slices;

process the check response messages to produce a second status level indication;

when the second status level indication is greater than the first status level indication, sending a new retrieval request for the decode threshold number of encoded data slices having the second status level indication to the second grouping of storage units of the DSN; and

when the second status level indication is substantially equal to the first status level indication, indicate that the decode threshold number of encoded data slices is of the common status level as the other encoded data slices.

10. The non-transitory computer readable storage medium of claim 9, wherein the one or more processing modules functions to execute the operational instructions stored by the at least one memory section to cause the one or more computing devices of the DSN to retrieve the decode threshold number of encoded data slices by:

receiving a first decode threshold number of encoded data slices;

determining whether each encoded data slice of the first decode threshold number of the encoded data slices have a same status level;

when each encoded data slice of the first decode threshold number of the encoded data slices have the same status level, using the first decode threshold number of encoded data slices as the decode threshold number of encoded data slices; and

when each encoded data slice of the first decode threshold number of the encoded data slices do not have the same status level,

receiving a second decode threshold number of encoded data slices; and

when each encoded data slice of the second decode threshold number of the encoded data slices have the same status level, using the second decode threshold number of encoded data slices as the decode threshold number of encoded data slices.

11. The non-transitory computer readable storage medium of claim 9 further comprises:

the at least one memory section stores further operational instructions that, when executed by the one or more processing modules, causes the one or more computing devices of the DSN to;

when the decode threshold number of encoded data slices is of the common status level as the other encoded data slices, decode the decode threshold number of encoded data slices to recover the data segment.

12. The non-transitory computer readable storage medium of claim 9 further comprises:

the at least one memory section stores further operational instructions that, when executed by the one or more processing modules, causes the one or more computing devices of the DSN to;

when the second status level indication is less than the first status level indication, determine whether to retrieve the decode threshold number of the other encoded data slices; and

when the determination is to retrieve the decode threshold number of the other encoded data slices;

retrieve the decode threshold number of the other encoded data slices; and

decode the decode threshold number of the other encoded data slices to recover the data segment having the second status level.

13. The non-transitory computer readable storage medium of claim 12 further comprises:

the at least one memory section stores further operational instructions that, when executed by the one or more processing modules, causes the one or more computing devices of the DSN to;

determine to retrieve the decode threshold number of the other encoded data slices based on one or more of;

data concurrency of the data object;

time concurrency of write requests of the data segment;

a request for all status levels of the data segment; and

user identifiers of the first and second status levels of the data segment.

14. The non-transitory computer readable storage medium of claim 13 further comprises:

the at least one memory section stores further operational instructions that, when executed by the one or more processing modules, causes the one or more computing devices of the DSN to;

decode the decode threshold number of the encoded data slices to recover the data segment having the first status level; and

when the decode threshold number of the other encoded data slices was retrieved based on the time concurrency of write requests of the data segment, merge changes of the data segment having the second status level indication into the data segment having the first status level indication.

15. The non-transitory computer readable storage medium of claim 9 further comprises:

a number of encoded data slices of the other encoded data slices is substantially equal to a read check number, wherein the read check number is in a range of numbers between the decode threshold number and the width number minus the decode threshold number.

16. The non-transitory computer readable storage medium of claim 9 further comprises:

the at least one memory section stores further operational instructions that, when executed by the one or more processing modules, causes the one or more computing devices of the DSN to;

when the second status level indication is not substantially equal to the first status level indication, determine whether to maintain in the first and second groupings of storage units encoded data slices having different status level indications or to update the encoded data slices having different status level indications.

17. A computing device of a group of computing devices of a dispersed storage network (DSN), the computing device comprises:

an interface;

a local memory; and

a processing module including a processor operably coupled to the interface and the local memory, wherein the processing module functions to;

retrieve, via the interface, a decode threshold number of encoded data slices of a set of encoded data slices from a first grouping of storage units of the DSN, wherein a data segment of a data object 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 includes the decode threshold number and a width number, wherein the decode threshold number corresponds to a minimum number of encoded data slices of the set of encoded data slices that are needed to recover the data segment, wherein the width number corresponds to a total number of encoded data slices in the set of encoded data slices, and wherein the decode threshold number is less than or equal to one-half of the width number; and

to verify that the decode threshold number of encoded data slices is of a common status level as other encoded data slices of the set of encoded data slices;

determine a first status level indication of the retrieved decode threshold number of encoded data slices;

send, via the interface, check status request messages to a second grouping of storage units of the DSN, wherein a check status request message of the check status request messages is requesting that a storage unit of the second grouping of storage units provide a status level indication of one of the other encoded data slices stored by the storage unit, wherein the second grouping of storage units store remaining encoded data slices of the set of encoded data slices, wherein the remaining encoded data slices is the total number of encoded data slices less the decode threshold number of encoded data slices;

receive, via the interface, check status response messages from the second grouping of storage units, wherein a check status response message of the check status response messages includes the status level indication of the one of the other encoded data slices;

process the check response messages to produce a second status level indication;

when the second status level indication is greater than the first status level indication, sending a new retrieval request for the decode threshold number of encoded data slices having the second status level indication to the second grouping of storage units of the DSN; and

when the second status level indication is substantially equal to the first status level indication, indicate that the decode threshold number of encoded data slices is of the common status level as the other encoded data slices.

18. The computing device of claim 17, wherein the processing module functions to retrieve the decode threshold number of encoded data slices by:

receiving, via the interface, a first decode threshold number of encoded data slices;

determining whether each encoded data slice of the first decode threshold number of the encoded data slices have a same status level;

when each encoded data slice of the first decode threshold number of the encoded data slices have the same status level, using the first decode threshold number of encoded data slices as the decode threshold number of encoded data slices; and

when each encoded data slice of the first decode threshold number of the encoded data slices do not have the same status level,

receiving, via the interface, a second decode threshold number of encoded data slices; and

when each encoded data slice of the second decode threshold number of the encoded data slices have the same status level, using the second decode threshold number of encoded data slices as the decode threshold number of encoded data slices.

19. The computing device of claim 17, wherein the processing module further functions to:

when the decode threshold number of encoded data slices is of the common status level as the other encoded data slices, decode the decode threshold number of encoded data slices to recover the data segment.

20. The computing device of claim 17, wherein the processing module further functions to:

when the second status level indication is less than the first status level indication, determine whether to retrieve the decode threshold number of the other encoded data slices; and

when the determination is to retrieve the decode threshold number of the other encoded data slices;

retrieve, via the interface, the decode threshold number of the other encoded data slices; and

decode the decode threshold number of the other encoded data slices to recover the data segment having the second status level.

21. The computing device of claim 20, wherein the processing module further functions to:

determine to retrieve the decode threshold number of the other encoded data slices based on one or more of;

data concurrency of the data object;

time concurrency of write requests of the data segment;

a request for all status levels of the data segment; and

user identifiers of the first and second status levels of the data segment.

22. The computing device of claim 21, wherein the processing module further functions to:

decode the decode threshold number of the encoded data slices to recover the data segment having the first status level; and

when the decode threshold number of the other encoded data slices was retrieved based on the time concurrency of write requests of the data segment, merge changes of the data segment having the second status level indication into the data segment having the first status level indication.

23. The computing device of claim 17 further comprises:

a number of encoded data slices of the other encoded data slices is substantially equal to a read check number, wherein the read check number is in a range of numbers between the decode threshold number and the width number minus the decode threshold number.

24. The computing device of claim 17, wherein the processing module further functions to:

when the second status level indication is not substantially equal to the first status level indication, determine whether to maintain in the first and second groupings of storage units encoded data slices having different status level indications or to update the encoded data slices having different status level indications.