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 byteaddressability 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.