In order to improve a data processing unit comprising a data network, a file server integrated into the data network and having a separate data memory for the server and comprising at least one primary data file system, in which data files stored on the server data memory are filed, with respect to its security in the case of failures and the access to the data files following any failure, it is suggested that the data files of the primary data file system be divided into at least two primary activity groups with a different hierarchical ranking by means of a primary hierarchical memory management in accordance with a primary activity criterion, that the memory management copy at least the data files of the primary activity group with a lowest ranking into at least one secondary data file system on a data memory of a data storage unit positioned subsequent to the server data memory and that the memory management generate metadata from the copied data files of the primary activity group with a lowest ranking.