1. A method comprising: mounting, by a data storage device, a data storage medium having information recorded thereon, where: the information is formatted in accordance with a self-describing format standard that includes a first write function and a first read function, the information includes a first dataset and a second dataset, and the first dataset includes a first file mark, an index, and an empty space interposed between the second dataset and a combination of the first file mark and the index; receiving, from a first application, a data block and a corresponding write command for writing the data block onto the data storage medium; and in response to receiving the write command: determining that the empty space is present in the first dataset, writing, by a second write function, the data block into the empty space, and writing a second file mark in the second dataset; wherein the empty space of the data storage medium is inaccessible to the first write function of the self-describing format standard.