Data files systems with hierarchical ranking for different activity groups

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, data files stored on the server data memory being filed in said data file system,
• at least one post-positioned data storage unit storing data in at least one secondary data file system said at least one post-positioned data storage unit comprising a first storage medium and a second storage medium,
• the data files of the primary data file system being divided into at least two primary activity groups with a different hierarchical ranking in accordance with a primary activity criterion by means of a primary hierarchical memory management, the memory management copying at least the data files of the primary activity group with a lowest ranking into said at least one secondary data file system onto one of said storage media of said post-positioned data storage unit,
• the memory management generating metadata from the copied data files of the primary activity group with a lowest ranking and storing the metadata on the primary data file system, each of the data files of the primary activity group with the lowest ranking having associated metadata wherein the associated metadata is managed under the same name as the associated data file and wherein the memory management, in response to an access to a first data file of the primary activity group:
• locates the first data file in the at least one secondary data file system using first metadata associated with the first data file, copies the first data file from the at least one secondary data file system to the primary data file system to make the first file available on the primary data file system for the access.