A file is initially created to have metadata and a data block allocation for direct mapping without access to any indirect blocks. Therefore file access performance is increased because the direct mapping eliminates delay otherwise caused by fetching one or more indirect blocks. When needed, the functionality enabled by indirect mapping is provided by creating an indirect mapping for the file and then accessing the file using the indirect mapping. When the functionality enabled by the indirect mapping is no longer needed, the file is reorganized to a direct mapping and then accessed using the direct mapping. For example, a container file for a network attached SCSI LUN is created and accessed without a performance degradation until conversion to an indirect mapping occurs automatically and seamlessly upon activation of a supplementary storage service such as a file-based snapshot copy and replication facility.