1. A computer-implemented method for backing up data, the method comprising: receiving, by a backup program executed by a processor, a request for backing up a directory of one or more files of a file system from a client; in response to the request, generating a backup data stream, including inserting a first directory application specific data format (ASDF) section into the backup data stream, the first directory ASDF section storing metadata describing the directory of the one or more files, after the first directory ASDF section, for each of the one or more files of the directory, inserting a child file object representing a corresponding file, wherein the file object includes a child file object header, at least one child ASDF section encoding data associated with the corresponding file, and a child file object trailer, wherein the child file object header and the child file object trailer include metadata describing the corresponding file, and inserting a second directory ASDF section, wherein the first and second directory ASDF sections indicate context information of the directory; and transmitting the backup data stream to a backup storage to be stored therein.