Optimizing B+-tree for PCM-based hybrid memory

Phase change memory (PCM) as a newly developed storage medium has many attractive properties such as non-volatility, byte addressability, high density and low energy consumption. Thus, PCM can be used to build non-volatile main memory databases. However, PCM's long write latency and high write energy bring challenges to PCM-based memory systems. In this paper, we propose an improvement over the B+-tree for PCM. Particularly, we consider the read/write tendency of leaf nodes. For write-intensive leaf nodes, we use an overflow-node technique to reduce PCM writes, while for read-intensive ones, we adjust the tree structure to remove overflow nodes to improve read performance. Our experimental results suggest that our proposal outperforms the traditional B+-tree and the overflow B+-tree.