An Approach of Spatial Usage Optimization for NVM-Based Storage System

The emergency of non-volatile memory (NVM) can effectively address the performance gap between computing and storage due to its superior performance characteristics, including byte-addressability, low access latency and power consumption. However, NVM currently has high price and relative small capacity due to the process technology. In order to use the NVM in a cost-effective way, it is essential to improve the space utilization of NVM-based storage system. But, traditional file systems are not suitable for NVM as they are designed for block devices which incurs a large number of internal fragmentation and reduces the space utilization of storage system. On the other hand, the existing NVM-based file systems mostly focus on improving the system performance, failing to take full advantage of the byte-addressability of NVM. In this paper, we propose a Last Page Sharing (LPS) mechanism to improve the space utilization of NVM-based storage system. LPS utilizes the byte-addressability of NVM, and stores multiple small files or the tail data of files in the shared page together. We implement the Last Page Sharing scheme in an existing NVM-based file system and conduct several experiments to compare with other file systems to evaluate its efficiency. Experimental results show that, our approach reduces the space as much as 20% compared with Ext3, Ext4 and PMFS on average.