While performance and quality of service are the main criteria for application data management on storage units, energy efficiency is increasingly being stated as an additional criterion for evaluation. Due to the increasing energy consumption of storage subsystems, improving their energy efficiency is an important issue. In this paper we present a novel approach to storage management whereby both mid-level (file placement) and low level (disk mode) aspects are controlled, in a tiered storage architecture. The proposed mechanism is based on policies, and it is implemented via fuzzy logic rules, in contrast to attempting to build a model of the storage subsystem. The inputs to the storage management system are high level (application), mid level (file system) and low level (disk access patterns) information. The effectiveness of our approach has been validated by means of a case study using a TPC-C benchmark modified to access file level data. Results from this simulation are presented.