XPMFS: A New NVM File System for Vehicle Big Data

How to improve the I/O speed of storage systems is crucial for the ability of vehicle big data to meet the demand of vehicular social networks. Non-volatile memory (NVM) is an effective method for improving the performance of storage systems. Meanwhile, metadata management efficiency has a significant impact on the I/O performance of storage systems. But the current metadata management strategy is not efficient and will decrease the endurance of NVM devices. We design a new file system with a distributed metadata management strategy for hybrid NVM consisting of NVDIMMs and PCIe NVM devices. Based upon the intrinsic characteristics of two types of NVM devices and different attributes in the metadata, the attributes are divided, reorganized, and distributed between the two types of NVM devices based on the access frequency. The basic attributes with high access frequency are stored in NVDIMMs and managed by the CPU using a hierarchical algorithm to ensure the efficiency of management. The extended attributes with low access frequency are converted to multiple key-value pairs to improve the scalability of management and are stored in the PCIe NVM devices. Then, the embedded processor in the PCIe NVM devices is used to manage these extended attributes in the form of key-value pairs. This can reduce the transfer between the CPU and the PCIe NVM devices and decrease the write amplification of the PCIe NVM devices as well as improve the efficiency of metadata management. Thus, the metadata management tasks can be distributed between the CPU and the embedded processor in the PCIe NVM devices to reduce the time overhead of metadata management. Finally, a prototype named XPMFS is implemented based on PMFS and PMBD. Fio and Filebench are used to test its performance against PMFS and Ext4-DAX on PMBD. For Ext4-DAX on PMBD, the results demonstrate that the XMPFS can reduce the write and read time overhead by 52% and 49%, respectively, improving the I/O performance by 1.5 times under real workloads. The I/O performance of XPMFS is only slightly inferior to that of PMFS, but it avoids the storage capacity limitation of PMFS and aims for hybrid NVM.