Detection of data affected by inaccessible storage blocks in a deduplication system

• US 10,042,854 B2
• Filed: 06/18/2015
• Issued: 08/07/2018
• Est. Priority Date: 06/18/2015
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Aronovich, Lior, Kredi, Amir
• Primary Examiner(s): PYO, MONICA M
• Application Number:
  US14/743,587
• Publication Number:
  US 20160371294A1
• Time in Patent Office: 1,146 Days
• Field of Search: 707692, 707756, 707693
• CPC Class Codes: G06F 16/1748 De-duplication implemented within the file system, e.g. based on file segments de-duplication techniques in storage systems for the management of data blocks G06F3/0641
• CPC Class Codes: G06F 16/245 Query processing

Abstract

Various embodiments for managing data in a data storage having data deduplication. In response to a portion of the data storage determined to be inaccessible, an identifier of a user data segment is queried by examining a corresponding back reference data structure, the back reference data structure implemented as an approximation of a relationship between the user data segment and a particular storage block in the data storage. If the outcome of the query is negative, the user data segment is determined not associated with the particular storage block. If the outcome of the query is positive, the user data segment is warranted be examined further to determine if the user data segment is associated with the particular storage block.

Claims

1. A method, performed by a processor, for managing data in a data storage having data deduplication, comprising:

to efficiently recover or reclaim failed data in the data storage, in response to a portion of the data storage determined to be inaccessible;

querying, by the processor, an identifier of a user data segment by examining a corresponding back reference data structure to determine if the user data segment references a particular storage block, the storage block being associated with both a reference counter and the identifier of the back reference data structure;

wherein;

if the outcome of the query is negative, the user data segment is determined not associated with the particular storage block, and

if the outcome of the query is positive, the user data segment is warranted be examined further to determine if the user data segment is associated with the particular storage block;

wherein further examining the user data segment includes performing;

inspecting metadata of the back reference data structure associated with the inaccessible portion of the data storage,

inspecting the identifier of the user data segment in the data storage, and

inspecting metadata of user data segments whose identifiers returned a positive query outcome for at least one of the back reference data structures associated with the inaccessible portion of the data storage, and wherein the metadata and the identifier of the user data segment is inspected to determine the association with the particular storage block in lieu of scanning all metadata of all user objects in the data storage thereby efficiently identifying the failed data for reclamation.

2. The method of claim 1, further including associating the storage block in the file system with the back reference data structure, the back reference data structure implemented to determine a relationship between the user data segment and the particular storage block in the data storage.

3. The method of claim 1, further including performing one of:

determining the user data segment as being associated with the particular storage block, and thereby references the particular storage block, and the user data segment, and

determining the user data segment as being not associated with the particular storage block, and thereby not referencing the particular storage block.

4. The method of claim 1, wherein further examining the user data segment includes inspecting metadata to determine if the particular storage block is referenced by the user data segment.

5. The method of claim 1, further including configuring a size of one or a plurality of back reference data structures to be accommodated in memory.

6. The method of claim 1, further including, pursuant to querying the identifier of a user data segment, loading the back reference data structure into the memory.

7. A system for managing data in a data storage having data deduplication, comprising:

a processor, operational in the data storage, wherein the processor, to efficiently recover or reclaim failed data in the data storage, in response to a portion of the data storage determined to be inaccessible;

queries an identifier of a user data segment by examining a corresponding back reference data structure to determine if the user data segment references a particular storage block, the storage block being associated with both a reference counter and the identifier of the back reference data structure;

further wherein;

if the outcome of the query is negative, the user data segment is determined not associated with the particular storage block, and

if the outcome of the query is positive, the user data segment is warranted be examined further to determine if the user data segment is associated with the particular storage block;

wherein further examining the user data segment includes performing;

inspecting metadata of the back reference data structure associated with the inaccessible portion of the data storage,

inspecting the identifier of the user data segment in the data storage, and

inspecting metadata of user data segments whose identifiers returned a positive query outcome for at least one of the back reference data structures associated with the inaccessible portion of the data storage, and wherein the metadata and the identifier of the user data segment is inspected to determine the association with the particular storage block in lieu of scanning all metadata of all user objects in the data storage thereby efficiently identifying the failed data for reclamation.

8. The system of claim 7, further including a data repository, in electrical communication with the processor, for storing the back reference data structure in memory.

9. The system of claim 7, wherein the processor associates the storage block in the file system with the back reference data structure, the back reference data structure implemented to determine a relationship between the user data segment and the particular storage block in the data storage.

10. The system of claim 7, wherein the processor one of:

determines the user data segment as being associated with the particular storage block, and thereby references the particular storage block, and the user data segment, and

determines the user data segment as being not associated with the particular storage block, and thereby not referencing the particular storage block.

11. The system of claim 7, wherein the processor, pursuant to further examining the user data segment, inspects metadata to determine if the particular storage block is referenced by the user data segment.

12. The system of claim 7, wherein the processor configures a size of one or a plurality of back reference data structures to be accommodated in memory.

13. The system of claim 7, wherein the processor, pursuant to querying the identifier of a user data segment, loads the back reference data structure into the memory.

14. A computer program product for managing data in a data storage having data deduplication, the computer program product comprising a non-transitory computer-readable storage medium having computer-readable program code portions stored therein, the computer-readable program code portions comprising:

a first executable portion that, to efficiently recover or reclaim failed data in the data storage, in response to a portion of the data storage determined to be inaccessible;

queries an identifier of a user data segment by examining a corresponding back reference data structure to determine if the user data segment references a particular storage block, the storage block being associated with both a reference counter and the identifier of the back reference data structure;

wherein;

if the outcome of the query is negative, the user data segment is determined not associated with the particular storage block, and

if the outcome of the query is positive, the user data segment is warranted be examined further to determine if the user data segment is associated with the particular storage block;

wherein further examining the user data segment includes performing;

inspecting metadata of the back reference data structure associated with the inaccessible portion of the data storage,

inspecting the identifier of the user data segment in the data storage, and

inspecting metadata of user data segments whose identifiers returned a positive query outcome for at least one of the back reference data structures associated with the inaccessible portion of the data storage, and wherein the metadata and the identifier of the user data segment is inspected to determine the association with the particular storage block in lieu of scanning all metadata of all user objects in the data storage thereby efficiently identifying the failed data for reclamation.

15. The computer program product of claim 14, further including a second executable portion that associates the storage block in the file system with the back reference data structure, the back reference data structure implemented to determine a relationship between the user data segment and the particular storage block in the data storage.

16. The computer program product of claim 14, further including a second executable portion that one of:

determines the user data segment as being associated with the particular storage block, and thereby references the particular storage block, and the user data segment, and

determines the user data segment as being not associated with the particular storage block, and thereby not referencing the particular storage block.

17. The computer program product of claim 14, wherein further including a second executable that, pursuant to examining the user data segment, inspects metadata to determine if the particular storage block is referenced by the user data segment.

18. The computer program product of claim 14, further including a second executable portion that configures a size of one or a plurality of back reference data structure to be accommodated in memory.

19. The computer program product of claim 14, further including a second executable portion that, pursuant to querying the identifier of a user data segment, loads the back reference data structure into the memory.