Resolving write conflicts in a dispersed storage network

• US 9,766,810 B2
• Filed: 02/01/2016
• Issued: 09/19/2017
• Est. Priority Date: 02/26/2013
• Status: Expired due to Fees

• Current Assignee: Pure Storage, Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Baptist, Andrew, Resch, Jason K.
• Primary Examiner(s): Homayounmehr, Farid
• Assistant Examiner(s): Torres-Diaz, Lizbeth
• Application Number:
  US15/011,807
• Publication Number:
  US 20160147453A1
• Time in Patent Office: 596 Days
• Field of Search: 713189, 713193, 726 4, 726 6, 726 21
• CPC Class Codes: G06F 11/1092 Rebuilding, e.g. when physically replacing a failing disk
• CPC Class Codes: G06F 11/2094 Redundant storage or storage space G06F11/2056 takes precedence
• CPC Class Codes: G06F 2211/1028 Distributed, i.e. distributed RAID systems with parity
• CPC Class Codes: G06F 3/06 Digital input from, or digital output to, record carriers , e.g. RAID, emulated record carriers or networked record carriers
• CPC Class Codes: G06F 3/0604 Improving or facilitating administration, e.g. storage management
• CPC Class Codes: G06F 3/0611 in relation to response time
• CPC Class Codes: G06F 3/0622 in relation to access
• CPC Class Codes: G06F 3/0629 Configuration or reconfiguration of storage systems
• 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]

Abstract

A method includes a storage unit receiving a respective write request of a first set of write requests, wherein the first set of write requests functions as a write lock request. The method further includes the storage unit determining whether the storage unit has writing of the data object currently locked. The method further includes the storage unit sending a write lock response regarding the data object. The method further includes the storage unit, when a number of write lock responses indicate a write lock of the data object for the computing device and the number is equal to or exceeds a write lock response threshold, receive respective write requests from each set of a plurality of sets of write requests, wherein the plurality of sets of write requests includes write requests for remaining sets of encoded data slices of the plurality of sets of encoded data slices.

Claims

1. A method for execution by a storage unit of a set of storage units in a dispersed storage network (DSN), the method comprises:

receiving, by the storage unit, a respective write request of a first set of write requests, wherein a first computing device sent the first set of write requests regarding a first set of encoded data slices of a plurality of sets of encoded data slices to the storage units of the DSN, wherein a data object is divided into a plurality of data segments and the plurality of data segments is dispersed storage error encoded to produce the plurality of sets of encoded data slices, wherein the first set of write requests functions as a write lock request for the entire data object;

determining, by the storage unit, whether the storage unit has writing of the data object currently locked;

sending, by the storage unit, a write lock response regarding the data object to the first computing device, wherein the write lock response is associated with a request to write a particular encoded data slice to storage;

when a number of write lock responses, associated with requests to write a particular encoded data slice to storage, indicate a write lock of the data object for the first computing device and the number is equal to or exceeds a write lock response threshold, receive, by the storage unit, respective write requests from each set of a plurality of sets of write requests, wherein the plurality of sets of write requests includes write requests for remaining sets of encoded data slices of the plurality of sets of encoded data slices;

receiving, substantially concurrently with the receiving of the respective write request of the first set of write requests, a second respective write request of another first set of write requests, wherein a second computing device sent the other first set of write requests regarding another first set of encoded data slices of a second plurality of sets of encoded data slices to the storage units of the DSN, wherein the second computing device divided the data object into a second plurality of data segments and dispersed storage error encoded the second plurality of data segments to produce the second plurality of sets of encoded data slices, wherein the other first set of write requests functions as a write lock request for the data object by the second computing device;

when the respective write request of the first set of write requests was received prior to the second respective write request of another first set of write requests, locking the data object for the first computing device and generating the write lock response indicating the write lock of the data object for the first computing device; and

when the respective write request of the first set of write requests was received after the second respective write request of another first set of write requests, locking the data object for the second computing device and generating the write lock response indicating the write lock of the data object for the second computing device.

2. The method of claim 1 further comprises:

sending the write lock response to the second computing device.

3. The method of claim 1 further comprises:

temporarily storing, by the storage unit, an encoded data slice of the first set of encoded data slices in response to receiving the respective write request of the first set of write requests.

4. The method of claim 1 further comprises:

when the number of write lock responses is less than the write lock response threshold, receiving, by the storage unit, a respective rollback request of set of rollback requests from the first computing device; and

deleting temporary storage of an encoded data slice of the first set of encoded data slices in response to receiving the respective rollback request.

5. The method of claim 1 further comprises:

in response to receiving one or more of the respective write requests from each set of the plurality of sets of write requests;

permanently storing an encoded data slice of the first set of encoded data slices; and

permanently storing a respective encoded data slice from each of at least some of the remaining sets of encoded data slices.

6. A storage unit for using in a dispersed storage network (DSN), the 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 respective write request of a first set of write requests, wherein a first computing device sent the first set of write requests regarding a first set of encoded data slices of a plurality of sets of encoded data slices to the storage units of the DSN, wherein a data object is divided into a plurality of data segments and the plurality of data segments is dispersed storage error encoded to produce the plurality of sets of encoded data slices, wherein the first set of write requests functions as a write lock request for the entire data object;

determine whether the storage unit has writing of the data object currently locked;

send, via the interface, a write lock response regarding the data object to the first computing device, wherein the write lock response is associated with a request to write a particular encoded data slice to storage;

when a number of write lock responses, associated with requests to write a particular encoded data slice to storage, indicate a write lock of the data object for the first computing device and the number is equal to or exceeds a write lock response threshold, receive, via the interface, respective write requests from each set of a plurality of sets of write requests, wherein the plurality of sets of write requests includes write requests for remaining sets of encoded data slices of the plurality of sets of encoded data slices;

receive, via the interface and substantially concurrently with receiving of the respective write request of the first set of write requests, a second respective write request of another first set of write requests, wherein a second computing device sent the other first set of write requests regarding another first set of encoded data slices of a second plurality of sets of encoded data slices to the storage units of the DSN, wherein the second computing device divided the data object into a second plurality of data segments and dispersed storage error encoded the second plurality of data segments to produce the second plurality of sets of encoded data slices, wherein the other first set of write requests functions as a write lock request for the data object by the second computing device;

when the respective write request of the first set of write requests was received prior to the second respective write request of another first set of write requests, lock the data object for the first computing device and generate the write lock response indicating the write lock of the data object for the first computing device; and

when the respective write request of the first set of write requests was received after the second respective write request of another first set of write requests, lock the data object for the second computing device and generate the write lock response indicating the write lock of the data object for the second computing device.

7. The storage unit of claim 6, wherein the processing module is further operable to

send, via the interface, the write lock response to the second computing device.

8. The storage unit of claim 6, wherein the processing module is further operable to:

temporarily store, in the memory, an encoded data slice of the first set of encoded data slices in response to receiving the respective write request of the first set of write requests.

9. The storage unit of claim 6, wherein the processing module is further operable to

when the number of write lock responses is less than the write lock response threshold, receive, via the interface, a respective rollback request of set of rollback requests from the first computing device;

and

delete temporary storage of an encoded data slice of the first set of encoded data slices in response to receiving the respective rollback request.

10. The storage unit of claim 6, wherein the processing module is further operable to:

in response to receiving one or more of the respective write requests from each set of the plurality of sets of write requests;

permanently store, in the memory, an encoded data slice of the first set of encoded data slices; and

permanently store, in the memory, a respective encoded data slice from each of at least some of the remaining sets of encoded data slices.

11. A non-transitory memory device comprises:

a first storage section that stores operational instructions that, when executed by a storage unit of a dispersed storage network (DSN), causes the storage unit to;

receive a respective write request of a first set of write requests, wherein a first computing device sent the first set of write requests regarding a first set of encoded data slices of a plurality of sets of encoded data slices to the storage units of the DSN, wherein a data object is divided into a plurality of data segments and the plurality of data segments is dispersed storage error encoded to produce the plurality of sets of encoded data slices, wherein the first set of write requests functions as a write lock request for the entire data object;

a second storage section that stores operational instructions that, when executed by the storage unit, causes the storage unit to;

determine whether the storage unit has writing of the data object currently locked; and

send a write lock response regarding the data object to the first computing device, wherein the write lock response is associated with a request to write a particular encoded data slice to storage;

a third storage section that stores operational instructions that, when executed by the storage unit, causes the storage unit to;

when a number of write lock responses, associated with requests to write a particular encoded data slice to storage, indicate a write lock of the data object for the first computing device and the number is equal to or exceeds a write lock response threshold, receive respective write requests from each set of a plurality of sets of write requests, wherein the plurality of sets of write requests includes write requests for remaining sets of encoded data slices of the plurality of sets of encoded data slices;

the first storage section further stores operational instructions that, when executed by the storage unit, causes the storage unit to;

receive, substantially concurrently with receiving of the respective write request of the first set of write requests, a second respective write request of another first set of write requests, wherein a second computing device sent the other first set of write requests regarding another first set of encoded data slices of a second plurality of sets of encoded data slices to the storage units of the DSN, wherein the second computing device divided the data object into a second plurality of data segments and dispersed storage error encoded the second plurality of data segments to produce the second plurality of sets of encoded data slices, wherein the other first set of write requests functions as a write lock request for the data object by the second computing device;

the second storage section that stores operational instructions that, when executed by the storage unit, causes the storage unit to;

when the respective write request of the first set of write requests was received prior to the second respective write request of another first set of write requests, lock the data object for the first computing device and generate the write lock response indicating the write lock of the data object for the first computing device; and

when the respective write request of the first set of write requests was received after the second respective write request of another first set of write requests, lock the data object for the second computing device and generate the write lock response indicating the write lock of the data object for the second computing device.

12. The non-transitory memory device of claim 11, wherein the third storage section further stores operational instructions that, when executed by the storage unit, causes the storage unit to:

send the write lock response to the second computing device.

13. The non-transitory memory device of claim 11, wherein the first storage section further stores operational instructions that, when executed by the storage unit, causes the storage unit to:

temporarily store an encoded data slice of the first set of encoded data slices in response to receiving the respective write request of the first set of write requests.

14. The non-transitory memory device of claim 11 further comprises:

a fourth storage section that stores operational instructions that, when executed by the storage unit, causes the storage unit to;

when the number of write lock responses is less than the write lock response threshold, receive a respective rollback request of set of rollback requests from the first computing device; and

delete temporary storage of an encoded data slice of the first set of encoded data slices in response to receiving the respective rollback request.

15. The non-transitory memory device of claim 11, wherein the first storage section further stores operational instructions that, when executed by the storage unit, causes the storage unit to:

in response to receiving one or more of the respective write requests from each set of the plurality of sets of write requests;

permanently store an encoded data slice of the first set of encoded data slices; and

permanently store a respective encoded data slice from each of at least some of the remaining sets of encoded data slices.