Restoring data from a storage device to a cloud

1. A method of restoring data from a storage device to a cloud service, comprising:

initializing each of a plurality of flags for each of a plurality of portions of the data when the data is initially recalled from the cloud service to the storage device, the flags indicating whether a corresponding portion of the data has been modified while being stored on the storage device;

copying a particular one of the portions to a storage pool in response to a corresponding one of the flags being in an initialized state and the particular one of the portions being modified;

modifying a particular one of the flags in response to a corresponding one of the portions being modified;

transferring to the cloud service only portions of the data having corresponding flags that have been modified to migrate; and

merging the portions of the data with remaining data at the cloud service, wherein data from portions that are transferred to the cloud service and merged is different from data of corresponding portions copied to the storage pool.

2. A method, according to claim 1 , wherein data that is recalled from the cloud service to the storage device is maintained on the cloud service.

3. A method, according to claim 2 , wherein the portions of data that are transferred from the storage device to the cloud service overwrite data maintained at the cloud service.

4. A method, according to claim 1 , further comprising:

retrieving a point-in-time version of the data using the flags and data in the storage pool.

5. A method, according to claim 1 , wherein the flags are Boolean values.

6. A method, according to claim 1 , wherein the flags are one of: a byte or an n-bit data word.

7. A method, according to claim 6 , wherein n is sixteen.

8. A non-transitory computer readable medium containing software that restores data from a storage device to a cloud service, the software comprising:

executable code that initializes each of a plurality of flags for each of a plurality of portions of the data when the data is initially recalled from the cloud service to the storage device, the flags indicating whether a corresponding portion of the data has been modified while being stored on the storage device;

executable code that copies a particular one of the portions to a storage pool in response to a corresponding one of the flags being in an initialized state and the particular one of the portions being modified;

executable code that modifies a particular one of the flags in response to a corresponding one of the portions being modified;

executable code that transfers to the cloud service only portions of the data having corresponding flags that have been modified to migrate; and

executable code that merges the portions of the data with remaining data at the cloud service, wherein data from portions that are transferred to the cloud service and merged is different from data of corresponding portions copied to the storage pool.

9. A non-transitory computer readable medium, according to claim 8 , wherein data that is recalled from the cloud service to the storage device is maintained on the cloud service.

10. A non-transitory computer readable medium, according to claim 9 , wherein the portions of data that are transferred from the storage device to the cloud service overwrite data maintained at the cloud service.

11. A non-transitory computer readable medium, according to claim 8 , further comprising:

executable code that retrieves a point-in-time version of the data using the flags and data in the storage pool.

12. A non-transitory computer readable medium, according to claim 8 , wherein the flags are Boolean values.

13. A non-transitory computer readable medium, according to claim 8 , wherein the flags are one of: a byte or an n-bit data word.

14. A non-transitory computer readable medium, according to claim 13 , wherein n is sixteen.