Restoration of a parent LUN through modification of a read-write clone LUN as the parent LUN

1. A machine implemented method for restoring a parent logical unit number (LUN) from a snapshot of the parent LUN, comprising:

transforming the snapshot of the parent LUN from a read-only state to a read-write clone LUN using a target module of a storage operating system;

changing a first data structure of a block transfer protocol to refer to the parent LUN as another clone LUN such that the parent LUN can be deleted after restoring the parent LUN;

modifying a second data structure of the block transfer protocol to refer to the read-write clone LUN as the parent LUN; and

restoring the parent LUN by presenting the read-write clone LUN as the parent LUN, when the modification of the second data structure is complete.

2. The method of claim 1 further comprising:

deleting the another clone LUN when the modification of the second data structure is complete.

3. The method of claim 1 , wherein the block transfer protocol comprises a small computer system interface (SCSI) target of a volume of a storage system, and wherein the snapshot is at least one of a point-in-time, a consistent image, and a read-only version of the parent LUN that corresponds to a physically addressable storage unit.

4. The method of claim 1 further comprising:

updating the first data structure to point at least one of a read request and a write request to a restored parent LUN created when the modification of the second data structure is complete.

5. The method of claim 1 , wherein the snapshot is a created through a deduplication operation in which unique data blocks of the parent LUN and the snapshot are stored in the volume of the storage system and a meta-data is created that references the unique data blocks.

6. The method of claim 5 wherein the snapshot is a read-only clone LUN presented to a host device as the snapshot of the parent LUN.

7. The method of claim 6 further comprising:

coalescing an identical data instance of the read-only clone LUN and the parent LUN in a data block of the volume of the storage system.

8. The method of claim 1 , wherein a machine is caused to perform the method of claim 1 when a set of instructions in a form of a machine-readable medium is executed by the machine.

9. A system comprising:

a host device having an initiator that requests a restoration of a parent LUN;

a network; and

a storage system coupled to the host device through the network to restore the parent LUN by transforming a read-only copy of the parent LUN as a read-write clone LUN and then marking the read-write clone LUN as the parent LUN for presenting the read-write clone LUN as the parent LUN;

wherein data structures of the parent LUN and the read-write clone LUN are switched so that the parent LUN is referenced as another clone LUN and the read-write clone LUN is referenced as the parent LUN to present the read-write clone LUN as the parent LUN; and wherein the parent LUN can be deleted by deleting the another clone LUN after restoring the parent LUN.

10. The system of claim 9 wherein the storage system to delete the parent LUN now marked as another clone LUN when the restoration is complete.

11. The system of claim 9 , wherein the read-write clone LUN is created from a snapshot of the previous parent LUN, and wherein the snapshot is at least one of a point-in-time, a consistent image, and the read-only clone LUN of the parent LUN that corresponds to a physically addressable storage unit.

12. The system of claim 11 , wherein the snapshot is a created through a deduplication operation in which unique data blocks of the parent LUN and the read-only clone LUN are stored in a volume of the storage system and a meta-data is created that references the unique data blocks.

13. The system of claim 12 wherein the snapshot is the read-only clone LUN presented to the host device as the snapshot of the parent LUN.

14. The system of claim 13 wherein an identical data instance of the read-only clone LUN and the parent LUN is coalesced in a data block of the volume of the storage system.

15. A machine implemented method for restoring a parent LUN (logical unit number) from a snapshot of the parent LUN, comprising:

modifying a first data structure of a block transfer protocol to refer to the parent LUN as another clone LUN such that the parent LUN can be deleted after being restored;

creating a restored parent LUN through a modification of a second data structure of the block transfer protocol to reference a read-write clone LUN as the parent LUN and presenting the read-write clone as the parent LUN; wherein the read-write clone LUN of the parent LUN is generated by transforming a read-only state of a read-only clone of the parent LUN to a read-write state;

marking a restoration operation as successful when the modification of the first data structure and the second data structure is complete; and

deleting the another clone LUN that refers to the parent LUN when the restoration operation is successful.

16. The method of claim 15 , wherein the block transfer protocol comprises a small computer system interface (SCSI) target of a volume of a storage system, and wherein the snapshot is at least one of a point-in-time, a consistent image, and a read-only version of the parent LUN that corresponds to a physically addressable storage unit.

17. The method of claim 15 further comprising:

updating the first data structure to point at least one of a read request and a write request to the restored parent LUN.

18. The method of claim 15 , wherein the snapshot is a created through a deduplication operation in which unique data blocks of the parent LUN and the snapshot are stored in the volume of the storage system and a meta-data is created that references the unique data blocks, and wherein the snapshot is a read-only clone LUN presented to a host device as the snapshot of the parent LUN.

19. The method of claim 15 further comprising:

coalescing an identical data instance of the read-only clone LUN and the parent LUN in a data block of the volume of the storage system.