US Patent 7653612 Data protection services offload using shallow files

A shallow file is adapted for intensive read-only access to data of a primary file. The primary file resides in another file system or file server. The shallow file includes the data block mapping metadata of the primary file and a link to the primary file. To open the shallow file, the file system manager of the shallow file obtains a read lock on the primary file from the file system manager of the primary file. Then the file system manager of the shallow file may use the data block mapping in the shallow file to access the file data from the primary file in storage without participation of the file system manager of the primary file. This permits offloading of data protection services for secure and efficient storage of a backup copy of the file data.