Storage system-based hole punching for reclaiming unused space from a data container

• US 8,086,652 B1
• Filed: 08/15/2007
• Issued: 12/27/2011
• Est. Priority Date: 04/27/2007
• Status: Active Grant

• Current Assignee: NetApp, Inc.
• Original Assignee: NetApp, Inc.
• Inventors: Pasupathy, Shankar, Goodson, Garth Richard, Kleiman, Steven R., Bisson, Timothy
• Primary Examiner(s): Breene, John E
• Assistant Examiner(s): Phillips, III, Albert
• Application Number:
  US11/838,966
• Time in Patent Office: 1,595 Days
• Field of Search: 707/823, 707/827
• US Class Current: 707/823
• CPC Class Codes: G06F 3/0608 Saving storage space on storage systems
• CPC Class Codes: G06F 3/0631 by allocating resources to storage systems
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]

Abstract

A system and method reclaims unused storage space from a data container, such as a logical unit number (LUN) of a storage system. In particular, a novel technique is provided that allows a storage system to reclaim storage space not used by a client file system for which the storage system maintains storage, without requiring assistance from the client file system to determine storage usage. In other words, storage system may independently reclaim storage space not used by the client file system, without that file system'"'"'s intervention.

Claims

1. A method for use by a storage system, comprising a processor and a memory, for reclaiming space unused by a client file system, the method comprising:

determining a storage mapping between client file system storage units and storage system storage units, wherein the client file system storage units are overlaid onto the storage system storage units;

determining a client file system representation of storage unit usage associated with the client file system storage units;

determining, by the storage system; and

without intervention from the client file system, unused client file system storage units;

correlating the unused client file system storage units with particular storage system storage units based on the storage mapping and the client file system representation of storage unit usage to determine that the particular storage system storage units are unused by the client file system; and

deallocating the particular storage system storage units correlated with the unused client file system storage units.

2. The method as in claim 1, wherein determining the storage mapping further comprises:

determining a client file system type of the client file system.

3. The method as in claim 2, wherein determining the storage mapping further comprises:

loading a boot sector of the client file system; and

determining the client file system type from the boot sector.

4. The method as in claim 2, wherein determining the storage mapping further comprises:

determining client file system specific information; and

determining a configuration of the client file system storage units based on the specific information.

5. The method as in claim 4, wherein determining the storage mapping further comprises:

determining a configuration of the storage system storage units; and

mapping the client file system storage units to the storage system storage units based on the configuration of the storage system storage units and the configuration of the client file system storage units.

6. The method as in claim 1, wherein the storage mapping comprises one or more storage system storage units corresponding to one or more client file system storage units.

7. The method as in claim 6, wherein the storage mapping comprises one storage system storage unit corresponding to a plurality of client file system storage units, the method further comprising:

deallocating the storage system storage unit if the corresponding plurality of client file system storage units are unused.

8. The method as in claim 6, wherein the storage mapping comprises a plurality of storage system storage units corresponding to a client file system storage unit that is unused, the method further comprising:

deallocating the plurality of storage system storage units for the corresponding client file system storage unit that is unused.

9. The method as in claim 6, wherein the storage mapping comprises a storage system storage unit corresponding to a client file system storage unit that is unused, the method further comprising:

deallocating the storage system storage unit for the corresponding client file system storage unit that is unused.

10. The method as in claim 1, wherein the client file system storage units on a storage system storage unit comprise a read-only image of the client file system.

11. The method as in claim 1, wherein the client file system storage units on a storage system storage unit comprise a persistent consistency point image (PCPI).

12. The method as in claim 1, wherein the client file system storage units are part of an inactive file system.

13. The method as in claim 1, wherein the client file system representation of storage unit usage associated with the client file system storage units is a bitmap.

14. The method as in claim 1, further comprising:

receiving a read request for a deallocated storage system storage unit; and

returning an indication that the deallocated storage system storage unit is deallocated.

15. The method as in claim 14, wherein the indication is data including all zeros.

16. The method as in claim 14, wherein the indication is a specific reply to the request that identifies the requested deallocated storage system storage unit as a deallocated storage unit.

17. The method as in claim 1, wherein the storage system storage units are physical blocks of storage that are mapped from virtual blocks of the storage system.

18. The method as in claim 17, further comprising:

removing a mapping from a virtual block to a deallocated storage system storage unit to prevent reading the deallocated storage system storage unit from the mapping from the virtual block.

19. The method as in claim 18, wherein the mapping is removed from a container file that holds the mapping.

20. The method as in claim 1, wherein the client file system is unaware of any deallocated storage system storage units.

21. The method as in claim 1, wherein the storage system storage units comprise at least one flexible volume.

22. A storage system for reclaiming space unused by a client file system, the storage system comprising:

a data container served by the storage system, the data container having one or more storage units;

a communication medium established with the client file system, wherein the client file system is overlaid onto the data container having the one or more storage units served by the storage system;

one or more processors configured to execute processes; and

a memory configured to store a hole punching process executable by each processor, the hole punching process when executed operable to determine a storage mapping between storage units of the client file system and storage units of the storage system, determine a client file system representation of storage unit usage associated with the storage units of the client file system to determine client file system storage units that are unused, without intervention from the client file system, correlate the unused client file system storage units with particular storage system storage units based on the storage mapping and the client file system representation of storage unit usage to determine that the particular storage system storage units are unused by the client file system, and deallocate the particular storage system storage units correlated with the unused client file system storage units.

23. A storage system, comprising a processor and a memory, for reclaiming space unused by a client file system, the storage system comprising:

a data container served by the storage system, the data container having one or more storage units;

means for overlaying the client file system onto the data container having the one or more storage units served by the storage system;

means for determining a storage mapping between storage units of the client file system and storage units of the storage system;

means for determining a client file system representation of storage unit usage associated with the client file system storage units;

means for determining for the storage system, without intervention from the client file system, unused client file system storage units;

means for correlating the unused client file system storage units with particular storage system storage units based on the storage mapping and the client file system representation of storage unit usage to determine that the particular storage system units are unused by the client file system; and

means for deallocating the particular storage system storage units correlated with the unused client file system storage units.

24. A method, comprising:

providing storage space on a storage system for a client file system overlaid onto the storage space on the storage system;

reclaiming, by the storage system comprising a processor and a memory, a particular storage space on the storage system not used by the client file system, without requiring intervention from the client file system, by correlating unused client file system storage units with the particular storage space on the storage system based on a storage mapping of the client file system with the storage system and a client file system representation.

25. The method as in claim 24, wherein used storage space is a read-only image of the client file system.