Research And Implementation Of A User Mode File System Based On NVM

As one of the important basic software,file system is the key technology supporting data center and cloud infrastructure in the era of big data.The file system based on the hard disk is quite mature in technology,but with the introduction and commercial use of new non-volatile storage devices with access performance close to the memory,there is a tendency to replace hard disks as the new underlying storage.However,traditional file system technology cannot effectively exert the performance and characteristics of non-volatile memory.How to solve the problems of low-performance complex software stacks,file system atomic semantics,and user-mode file system metadata synchronization costs that exist in the combination of the two has become a new research hotspot,and has become a new challenge for academic and industrial circles.In order to give full play to the performance of non-volatile memory,eliminate user-mode file system metadata synchronization overhead,and provide reliable file system atomic semantics,a new file system Unvm FS with full user-mode access is proposed.Unvm FS designs a non-volatile storage allocator to manage metadata and data,and each process in the user mode independently updates the metadata,eliminating the communication overhead between the central metadata module and the user process.The persistent metadata design can also save the time of system reconstruction and recovery after power failure or normal restart of the file system,which can be used after restart.In view of the problem that non-volatile memory byte addressing cannot guarantee the atomic semantics of the file system,Unvm FS designs a log structure data update mechanism to perform atomic updates on files,and a lightweight pre-write log mechanism to ensure the atomicity of directory operations and maintain file system data and Metadata consistency.Based on the real non-volatile memory(Intel Optane DC Persistent Memory),a prototype of the Unvm FS system was implemented,and the system was tested using filebench,an authoritative file system testing tool.In the basic read and write Microbenchmark load test,Unvm FS has a 15% to 35% increase in write bandwidth compared to the newly released libnvmmio in 2020,and a 27% to 182% increase in read and write bandwidth compared to nova and ext4-dax.The Macrobenchmark load test that simulates real access shows that Unvm FS is 16% to 134% higher than libnvmmio,and 18%to 214% higher than nova and ext4-dax.Experimental results show that the design improvement of Unvm FS is feasible and effective.