NVMCFS: Complex File System for Hybrid NVM

Due to the price limitation and the number of DIMM slot, Byte and Block addressable NVM devices should coexist in the massive Storage Class Memory(SCM). But they have many differences such as interface, access granularity, I/O performance and storage capacity. Therefore, the existing main memory and file system management algorithms cannot be applied in it directly. In this paper, we present a complex file system named NVMCFS for Hybrid NVM. The head-tail layout and space management based on two layer radix-tree is provided to unify logic space between two type NVM devices. The complex file structures, dynamic file data distributed strategy, buffer for an individual file and asymmetric call in strategy are used to speed up the access response and improve I/O performance. The hybrid consistent mechanism is given and it can reduce the performance loss NVMCFS. Finally, the prototype of NVMCFS is implemented and evaluated by various benchmark. Compared to Ext2 and Ext4 on PMBD, NVMCFS improves sequential read speed 4.4x and 5x, sequential write speed 2.8x and 1.9x, IOPS 45% and 62%, and has the similar I/O performance with PMFS. At the same time, NVMCFS reduces the total overhead of consistency by 50%~92% compared to Ext4.