Reversible data modifications within DS units

• US 10,120,574 B2
• Filed: 11/21/2016
• Issued: 11/06/2018
• Est. Priority Date: 06/25/2012
• Status: Expired due to Fees

• Current Assignee: Pure Storage, Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Baptist, Andrew D., Kazi, Asimuddin, Leggette, Wesley B., McShane, Niall J., Motwani, Manish, Resch, Jason K., Volvovski, Ilya
• Primary Examiner(s): Ko, Chae M
• Application Number:
  US15/357,622
• Publication Number:
  US 20170075585A1
• Time in Patent Office: 715 Days
• Field of Search: 714 622
• CPC Class Codes: G06F 11/008 Reliability or availability analysis
• CPC Class Codes: G06F 11/10 Adding special bits or symbols to the coded information, e.g. parity check, casting out 9's or 11's
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• CPC Class Codes: G06F 11/1092 Rebuilding, e.g. when physically replacing a failing disk
• CPC Class Codes: G06F 2201/81 Threshold
• CPC Class Codes: G06F 2211/109 Sector level checksum or ECC, i.e. sector or stripe level checksum or ECC in addition to the RAID parity calculation
• CPC Class Codes: G06F 3/0605 by facilitating the interaction with a user or administrator
• 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 3/0659 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: H03M 13/1515 Reed-Solomon codes
• CPC Class Codes: H03M 13/3761 using code combining, i.e. using combining of codeword portions which may have been transmitted separately, e.g. Digital Fountain codes, Raptor codes or Luby Transform [LT] codes

Abstract

A method includes sending a set of destructive modification requests to a set of storage units regarding a set of encoded data slices. The method further includes determining, by each storage unit of a decode threshold number of storage units of the set of storage units, whether to preserve a respective corresponding one of the decode threshold number of encoded data slices prior to executing a corresponding one of the set of destructive modification requests. When determined to preserve the respective corresponding one of the decode threshold number of encoded data slices, determining, by a first storage unit of the decode threshold number of storage units, to flag a first encoded data slice of the decode threshold number of encoded data slices or temporarily store a copy of the first encoded data slice. When determined to flag the first encoded data slice, flagging the first encoded data slice as preserved.

Claims

1. A method comprises:

sending, by a computing device of a dispersed storage network (DSN), a set of destructive modification requests to a set of storage units of the DSN regarding a set of encoded data slices, wherein a data segment of a data object is dispersed storage error encoded to produce the set of encoded data slices, wherein a decode threshold number of encoded data slices of the set of encoded data slices is needed to recover the data segment;

determining, by each storage unit of a decode threshold number of storage units of the set of storage units, whether to preserve a respective corresponding one of the decode threshold number of encoded data slices prior to executing a corresponding one of the set of destructive modification requests;

when determined to preserve the respective corresponding one of the decode threshold number of encoded data slices prior to executing the corresponding one of the set of destructive modification requests, determining, by a first storage unit of the decode threshold number of storage units, to flag a first encoded data slice of the decode threshold number of encoded data slices or temporarily store the first encoded data slice, wherein the first encoded data slice is the respective corresponding one of the decode threshold number of encoded data slices of the first storage unit; and

when determined to flag the first encoded data slice, flagging, by the first storage unit, the first encoded data slice as preserved.

2. The method of claim 1, wherein a destructive modification request of the set of destructive modification requests comprises one of:

a delete type;

an overwrite type;

a modification type; and

a new revision type.

3. The method of claim 1, wherein the determining to preserve the corresponding one of the decode threshold number of encoded data slices is based on one or more of:

a request type;

a requesting entity ID;

a priority indicator;

a certainty level indicator; and

a memory availability level indicator.

4. The method of claim 1 further comprises:

when determined not to preserve the respective corresponding one of the decode threshold number of encoded data slices, executing, by each storage unit of a decode threshold number of storage units of the set of storage units, the corresponding one of the set of destructive modification requests.

5. The method of claim 1 further comprises:

when determined to temporarily store the first encoded data slice, storing a copy of the first encoded data slice in temporary memory and executing the corresponding one of the set of destructive modification requests on the first encoded data slice.

6. The method of claim 5 further comprises:

deleting the copy of the first encoded data slice from the temporary memory after expiration of a time period.

7. The method of claim 1 further comprises:

when determined to temporarily store the first encoded data slice, moving the first encoded data slice to temporary memory.

8. The method of claim 7 further comprises:

executing the corresponding one of the set of destructive modification requests on the first encoded data slice stored in temporary memory after expiration of a time period.

9. The method of claim 1 further comprises:

executing the corresponding one of the set of destructive modification requests on the first encoded data slice flagged as preserved after expiration of a time period.

10. A computer readable memory comprises:

a first memory element that stores operational instructions that, when executed by a computing device of a dispersed storage network (DSN), cause the computing device to;

send a set of destructive modification requests to a set of storage units of the DSN regarding a set of encoded data slices, wherein a data segment of a data object is dispersed storage error encoded to produce the set of encoded data slices, wherein a decode threshold number of encoded data slices of the set of encoded data slices is needed to recover the data segment; and

a second memory element that stores operational instructions that, when executed by the set of storage units, cause the set of storage units to;

determine, by each storage unit of a decode threshold number of storage units of the set of storage units, whether to preserve a respective corresponding one of the decode threshold number of encoded data slices prior to executing a corresponding one of the set of destructive modification requests;

when determined to preserve the respective corresponding one of the decode threshold number of encoded data slices prior to executing the corresponding one of the set of destructive modification requests, determine, by a first storage unit of the decode threshold number of storage units, to flag a first encoded data slice of the decode threshold number of encoded data slices or temporarily store a copy of the first encoded data slice, wherein the first encoded data slice is the respective corresponding one of the decode threshold number of encoded data slices of the first storage unit; and

when determined to flag the first encoded data slice, flag, by the first storage unit, the first encoded data slice as preserved.

11. The computer readable memory of claim 10, wherein a destructive modification request of the set of destructive modification requests comprises one of:

a delete type;

an overwrite type;

a modification type; and

a new revision type.

12. The computer readable memory of claim 10, wherein the second memory element further stores operational instructions that, when executed by set of storage units, cause the set of storage units to determine to preserve the corresponding one of the decode threshold number of encoded data slices based on one or more of:

a request type;

a requesting entity ID;

a priority indicator;

a certainty level indicator; and

a memory availability level indicator.

13. The computer readable memory of claim 10, wherein the second memory element further stores operational instructions that, when executed by set of storage units, cause the set of storage units to:

when determined not to preserve the respective corresponding one of the decode threshold number of encoded data slices, execute, by each storage unit of a decode threshold number of storage units of the set of storage units, the corresponding one of the set of destructive modification requests.

14. The computer readable memory of claim 10, wherein the second memory element further stores operational instructions that, when executed by set of storage units, cause the set of storage units to:

when determined to temporarily store the first encoded data slice, store a copy of the first encoded data slice in temporary memory and execute the corresponding one of the set of destructive modification requests on the first encoded data slice.

15. The computer readable memory of claim 14, wherein the second memory element further stores operational instructions that, when executed by set of storage units, cause the set of storage units to:

delete the copy of the first encoded data slice from the temporary memory after expiration of a time period.

16. The computer readable memory of claim 10, wherein the second memory element further stores operational instructions that, when executed by set of storage units, cause the set of storage units to:

when determined to temporarily store the first encoded data slice, move the first encoded data slice to temporary memory.

17. The computer readable memory of claim 16, wherein the second memory element further stores operational instructions that, when executed by set of storage units, cause the set of storage units to:

executing the corresponding one of the set of destructive modification requests on the first encoded data slice stored in temporary memory after expiration of a time period.

18. The computer readable memory of claim 10 wherein the second memory element further stores operational instructions that, when executed by set of storage units, cause the set of storage units to:

execute the corresponding one of the set of destructive modification requests on the first encoded data slice flagged as preserved after expiration of a time period.