A fifty-percent rule to minimize the energy consumption of PCM-based storage systems

In recent years, phase-change memory (PCM) has drawn a lot of attention because of its byte-addressability and non-volatility. It has become a good alternative storage medium to reduce the performance gap between main memory and secondary storage, but its high energy consumption on writes is a challenging issue in the design of battery-powered mobile computing systems. By utilizing the byte-addressability and the asymmetric read-write energy/latency of PCM, we propose an energy-efficient update scheme with a fifty-percent rule for journaling file systems to reduce the energy consumption. This scheme only writes the modified data, instead of the whole updated block, to PCM-based storage devices with the guarantee of the sanity/integrity of file systems even if the system crashes or power failure occurs during the process of data updates. A series of experiments based on the implementation on the Linux system was conducted to evaluate the capability of the proposed scheme, and the results are very encouraging.