Efficient Space Management and Wear Leveling for PCM-Based Storage Systems

Phase change memory (PCM) has emerged as a promising candidate for next-generation storage media, owing to its low power consumption, non-volatility, and high scalability. However, PCM has limited write endurance, or more particularly, it can only undergo a limited number of write operations. This problem is much critical to the lifetime of PCM. Aiming to solve this problem, in this paper we propose an efficient space management scheme for PCM-based storage systems, which is able to level the write operations to PCM and lengthen the lifetime of PCM. In particular, we propose a new structure (called dual dynamic bucket lists) to manage the spaces of PCM, and further devise an efficient page management policy for page allocation, migration, and swaps. With these mechanisms, write operations are distributed to PCM chips in a balanced manner and the write amplification ratio of PCM incurred by page swaps is decreased, yielding less write operations to PCM and longer lifetime of PCM. Our experimental results on a simulated PCM-based device show that our proposal is effective in lengthening the lifetime of PCM, and thus offers a more practical solution for the space management on PCM-based storage systems.