File systems image transfer between dissimilar file systems

The invention provides techniques for duplicating all or part of a file system while maintaining consistent copies of the file system. A preferred embodiment reads data from the source file system (mapped according to a first storage block arrangement) creates an image stream and writes this data onto the destination file system (in accordance with a second storage block arrangement). Thus, the invention allows an image transfer between file systems that have dissimilar characteristics. An intermediate storage medium can be used to store or transmit the data read from the source file system before writing the data to the destination file system. (For example, the intermediate storage medium can include a magnetic tape or other archival device, or a network.) Another aspect of the invention writes the data to the intermediate storage medium using a normalized or implied block list. The information is read from the intermediate storage medium using normalized or implied block list and written to the destination file system according to the second storage block arrangement. Another aspect of the invention is that the invention determines a first set of block numbers (BNs), determines where the blocks referenced by these BNs are to be stored, and updates the BNs accordingly.