Patent ID: 7558929

Claim:
A method to create a copy of data in a cache memory associated with a storage system by an instant copy process (“ICP”), the method comprising the steps of: maintaining, in the cache memory, a first descriptor associated with a first partition and a second descriptor associated with a second partition, the first partition associated with a source logical unit and the second partition associated with a target logical unit; maintaining in the first descriptor a first array of fields representative of physical addresses of data blocks associated with the first partition; maintaining in the second descriptor a second array of fields representative of physical addresses of data blocks associated with the second partition; receiving a request to write given data blocks associated with at least one of the first partition and the second partition; in response to the request, establishing an ICP between the first partition and the second partition by setting ICP flags in the first descriptor and the second descriptor indicating the first partition and the second partition are undergoing a copy-on-write operation; dissociating the given data blocks currently associated with the second partition by setting respective data block flags in the second descriptor; copying the given data blocks of the first partition in the cache memory from the first partition to the second partition in the cache memory by updating fields of corresponding blocks in the second descriptor; triggering a fetch task to sequentially fetch all blocks of the first partition not in the cache memory module from one or more storage units in the storage system and copy all fetched blocks from the first partition to the second partition; while performing the fetch task, coherently handling incoming input/output (IO) requests directed to at least one of the first partition and the second partition; and on completion of the fetch task, setting the ICP flags to indicate that the first partition and the second partition have completed the ICP.