An autonomous data storage device for storing data files via an external file interface, the external file interface being controllable from an external device, the device comprising: a physical file storage for homogenous storage of files; the external file interface configured to allow sector level access to at least part of the physical file storage to support standard operating file system calls; an internal sector policy management unit located in between the external file interface and the physical file storage for sector level policy enforcement of the physical file storage, for one or more of the sector level managed sectors, the unit having an input for receiving instructions from the external file interface for sector oriented operations, and being configured to carry out sector policy management operations in accordance with.