WRITING DATA AVOIDING WRITE CONFLICTS IN A DISPERSED STORAGE NETWORK

• US 20140075112A1
• Filed: 08/05/2013
• Published: 03/13/2014
• Est. Priority Date: 09/13/2012
• Status: Active Grant

• Current Assignee: Pure Storage, Inc.
• Original Assignee: Cleversafe Incorporated (International Business Machines Corporation)
• Inventors: Baptist, Andrew, Dhuse, Greg, Volvovski, Ilya
• Granted Patent: US 9,424,326 B2
• Time in Patent Office: Days
• US Class Current: 711/114
• CPC Class Codes: G06F 16/178 Techniques for file synchronisation in file systems
• 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 16/278 Data partitioning, e.g. horizontal or vertical partitioning
• CPC Class Codes: G06F 3/0619 in relation to data integrity, e.g. data losses, bit errors
• 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: G06F 3/0689 Disk arrays, e.g. RAID, JBOD
• 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 by a first device of a dispersed storage network (DSN) sending a set of write revision requests to storage units of the DSN. The method continues with one of the storage units generating a write revision response regarding a potential write conflict issue. The method continues with the first device receiving the write revision responses to produce a set of received write revision responses and interpreting the set of received write revision responses to determine whether a write conflict issue exists. When the write conflict issue exists, the method continues with the first device issuing a set of write roll back requests to the storage units. When the write conflict issue does not exist, the method continues with the first device issuing a set of next phase write requests to the storage units regarding storing revised encoded data slices.

Claims

1. A method comprises:

sending, by a first device of a dispersed storage network (DSN), a set of write revision requests to storage units of the DSN, wherein a write revision request of the set of write revision requests includes a slice name and a revision number corresponding to a revision level of a revised encoded data slice;

generating, by one of the storage units, a write revision response regarding a potential write conflict issue based on the revision number;

receiving, by the first device, the write revision responses from at least some of the storage units to produce a set of received write revision responses;

interpreting, by the first device, the set of received write revision responses to determine whether a write conflict issue exists;

when the write conflict issue exists, issuing, by the first device, a set of write roll back requests to the storage units regarding aborting storage of respective revised encoded data slices; and

when the write conflict issue does not exist, issuing, by the first device, a set of next phase write requests to the storage units regarding storing the respective revised encoded data slices.

2. The method of claim 1, wherein the sending the set of write revision requests further comprises:

including the revised encoded data slice of the respective revised encoded data slices in the write revision request.

3. The method of claim 1, wherein the issuing the set of next phase write requests further comprises:

including the revised encoded data slice of the respective revised encoded data slices in one of the set of next phase write requests.

4. The method of claim 1 further comprises:

generating, by the one of the storage units, the write revision response to include a list of revision numbers that corresponds to a number of revised encoded data slices having the slice name that the one of the storage units is storing; and

interpreting, by the first device, the lists of revision numbers of the set of received write revision responses in view of the revision number by;

comparing a most recent revision number of the lists of revision numbers to the revision number; and

when at least a decode threshold number of the lists of revision numbers compare favorably to the revision number, indicating that the write conflict issue does not exist.

5. The method of claim 1 further comprises:

generating, by the one of the storage units, the write revision response to include a most recent revision number corresponding to a most recently stored one of the respective revised encoded data slices; and

interpreting, by the first device, the most recent revision numbers of the set of received write revision responses in view of the revision number and when at least a decode threshold number of the most recent revision numbers compare favorably to the revision number, indicating that the write conflict issue does not exist.

6. The method of claim 1 further comprises:

generating, by the one of the storage units, the write revision response to include a favorable or unfavorable revision number indication; and

interpreting, by the first device, the set of received write revision responses by indicating that the write conflict issue does not exist when at least a decode threshold number of favorable revision number indications were received.

7. The method of claim 6 further comprises:

comparing, by the one of the storage units, a most recent revision number corresponding to a most recently stored one of the respective revised encoded data slices to the revision number;

when the most recent revision number is less than the revision number, indicating, by the one of the storage units, the favorable revision number indication; and

when the most recent revision number is greater than or equal to the revision number, indicating, by the one of the storage units, the unfavorable revision number indication.

8. The method of claim 1 further comprises:

locking, by the one of the storage units, the slice name for a corresponding one of the set of write revision requests; and

while the slice name is locked for the corresponding one of the set of write revision requests;

receiving, by the one of the storage units from a second device of the DSN, a second write revision request regarding the slice name; and

sending, by the one of the storage units, a write error message to the second device.

9. A dispersed storage network (DSN) comprises:

a first module, when operable within a first device of the DSN, causes the first device to send a set of write revision requests to storage units of the DSN, wherein a write revision request of the set of write revision requests includes a slice name and a revision number corresponding to a revision level of a revised encoded data slice;

a second module, when operable within one of the storage units, causes the one of the storage units to generate a write revision response regarding a potential write conflict issue based on the revision number;

a third module, when operable within the first device, causes the first device to interpret a set of received write revision responses to determine whether a write conflict issue exists, wherein the first device received the write revision responses from at least some of the storage units to produce the set of received write revision responses; and

a fourth module, when operable within the first device, causes the first device to;

issue a set of write roll back requests to the storage units regarding aborting storage of respective revised encoded data slices when the write conflict issue exists; and

issue a set of next phase write requests to the storage units regarding storing the respective revised encoded data slices when the write conflict issue does not exist.

10. The DSN of claim 9, wherein the first module further functions to send the set of write revision requests by:

including the revised encoded data slice of the respective revised encoded data slices in the write revision request.

11. The DSN of claim 9, wherein the fourth module further functions to issue the set of next phase write requests by:

including the revised encoded data slice of the respective revised encoded data slices in one of the set of next phase write requests.

12. The DSN of claim 9 further comprises:

the second module functions to generate the write revision response to include a list of revision numbers that corresponds to a number of revised encoded data slices having the slice name that the one of the storage units is storing; and

the third module functions to interpret the lists of revision numbers of the set of received write revision responses in view of the revision number by;

comparing a most recent revision number of the lists of revision numbers to the revision number; and

when at least a decode threshold number of the lists of revision numbers compare favorably to the revision number, indicating that the write conflict issue does not exist.

13. The DSN of claim 9 further comprises:

the second module functions to generate the write revision response to include a most recent revision number corresponding to a most recently stored one of the respective revised encoded data slices; and

the third module functions to interpret the most recent revision numbers of the set of received write revision responses in view of the revision number and when at least a decode threshold number of the most recent revision numbers compare favorably to the revision number, indicating that the write conflict issue does not exist.

14. The DSN of claim 9 further comprises:

the second module functions to generate the write revision response to include a favorable or unfavorable revision number indication; and

the third module functions to interpret the set of received write revision responses by indicating that the write conflict issue does not exist when at least a decode threshold number of favorable revision number indications were received.

15. The DSN of claim 14 further comprises:

the second module further functions to;

compare a most recent revision number corresponding to a most recently stored one of the respective revised encoded data slices to the revision number;

indicate the favorable revision number indication when the most recent revision number is less than the revision number; and

indicate the unfavorable revision number indication when the most recent revision number is greater than or equal to the revision number.

16. The DSN of claim 9 further comprises:

the second module further functions to;

lock the slice name for a corresponding one of the set of write revision requests; and

while the slice name is locked for the corresponding one of the set of write revision requests;

receive, from a second device of the DSN, a second write revision request regarding the slice name; and

send a write error message to the second device.