A header data storage unit stores therein header data that identifies each file. A header data reader reads the stored header data, from the header data of the first file written to a magnetic tape to the header data of a target file, in order in which the files have been written to the magnetic tape. Based on the number of files whose header data have been read, an input/output controller controls positioning of a magnetic head.

Magnetic tape read channel signal values are developed employing intermediate bits of the path memory of a PRML Viterbi detector. Identification logic identifies a most likely path memory state of the PRML Viterbi detector from the path metrics of the PRML Viterbi detector. An intermediate bit sequence of the identified most likely path memory state is obtained, the intermediate bit sequence extending from an initiation point of the path memory which is intermediate the output and the input of the PRML Viterbi detector. A sample value is determined which corresponds to the obtained intermediate bit sequence.

A storage library is provided for formatting a mobile data storage element, such as a tape, with a first space dedicated for clear text or text as received by a host, such as an Independent Software Vender, wherein the first space is intended to accommodate header information which includes attributes about the mobile storage element. The data storage element is also formatted with a second space for storing encrypted or conditioned user data. The storage library further generally includes an encryption engine for encrypting data received from a host computer, a plurality of data storage elements, and at least two drives for storing data on the data storage elements.