Research And Design Of NAND FLASH File System Based On VxWorks Platform

Currently,the VxWorks platform uses TFFS as the FLASH management layer,the main function of TFFS is to shield the characteristics of Flash devices,and to provide a unified disk interface to the upper layer.DosFs file system can be run on the TFFS layer without modification.TFFS provides multiple flash translation layers to manage different Flash devices,where NFTL is used to manage NAND Flash devices.However,the implementation of NFTL is based on the small capacity of NAND Flash device,and therefore can not be directly applied to the large capacity of Flash NAND device.Based on the research of the working mechanism of TFFS and the defects of NFTL for large capacity NAND Flash,this paper proposes a solution of TFFS file system for large capacity NAND Flash.The solution contains two parts:the first part is implementation of device driver;the second part is NFTL optimization.Through the optimization,the NFTL can support large capacity NAND flash device well.This paper using page level address mapping to ensure that the page within the physical block is written sequentially which in line with the requirements of large capacity NAND Flash devices.By dividing the hot and cold data,hot and cold data can be store separately,which improve wear leveling.Reduce the number of updates to the NAND Flash device by using the hot data buffer,improve the write performance,and extend the life span of the device.To improve the loading speed of the equipment by using the checkpoint mechanism,avoid the multiple scanning of the NAND Flash.FlashSim evaluation of the NFTL optimization algorithm shows that the optimization of the NFTL provides better read and write performance,better wear leveling and less address mapping overhead.This paper further compares the optimization of NFTL and the original NFTL performance in the Loongson 1B platform.The experimental results are consistent with the evaluation results of FlashSim.In summary,this solution can effectively overcome original TFFS'defects,and provide better I/O performance and better wear leveling effect.