Patent ID: 7546431

Claim:
A method comprising: a read-write snapshot copy facility creating a read-write snapshot copy of at least a portion of a production file system by creating stub files including pointers to data files in a read-only snapshot copy of at least the portion of the production file system; and the read-write snapshot copy facility responding to a read request from an application program to read data from a read-write snapshot copy of at least a portion of one of the data files in the read-only snapshot copy of at least the portion of the production file system by accessing one of the stub files to obtain a pointer to said one of the data files, and using the pointer to said one of the data files to read data from said one of the data files and to return the data read from said one of the data files to the application program; and the read-write snapshot copy facility responding to a write request from the application program to write data to a read-write snapshot copy of at least a portion of another of the data files in the read-only snapshot copy of at least the portion of the production file system by accessing another of the stub files to obtain a pointer to said another of the data files, and using the pointer to said another of the data files to read data from said another of the data files to produce a file that is written to by the application program and that replaces said another of the stub files.