Patent ID: 8015376

Claim:
A method for managing copies of a mapped storage volume in a storage system having a plurality of physical blocks with each physical block having a corresponding physical block address, the method comprising: generating a first copy of the mapped storage volume comprising a plurality of logical blocks each mapped to a corresponding physical block; copying the first copy to generate a second copy of the mapped storage volume; associating ancestral meta-data with the first copy and with the second copy to identify an ancestral relationship between the first copy and the second copy; associating reference meta-data with each physical block, wherein the reference meta-data indicates which copies of the mapped storage volume may access the corresponding physical block, wherein the reference meta-data comprising a possible reference bitmask and an explicit reference bitmask; and executing a write request that modifies content of an identified logical block of an identified copy of the mapped storage volume, wherein the identified logical block is associated with a corresponding identified physical block, wherein the execution is based on a function of the ancestral meta-data associated with the identified copy and the reference meta-data associated with the corresponding identified physical block, and wherein the execution assures other copies of the mapped storage volume retain access to original content of the corresponding identified physical block as it exists prior to the execution of the write request.