The Design And Realization Of NAND Flash-based Filesystem

With the development and popularity of embedded system, computer and consume digita products, non-volatile NAND Flash has become the main storage medium in a variety of embedded mobile platforms and consume digital products. NAND Flash has low power consumption, fast read and write output, large capacity, low cost, earthquake and resistant to earthquake and corrosion. With the increasing capacity of Nand Flash, how to manage files which were stored in the NAND Flash has become a hot spot of a computer science research. The priorities technology of NAND Flash file system research are the file system mount speed, the method of file organization, garbage collection and wear leveling.Currently, the most popular and successful NAND Flash file system are YAFFS, JFFS, UBIFS. The highest stability and widely used is YAFFS file system. However, in the course of the YAFFS emerged two shortcomings:1) The mount speed depands on NAND Flash capacity and the quantity of the files stored on Flash.2) The YAFFS file system does not consider wear leveling of the NAND Flash when process the garbage collector, therefore it can not be effective in prolonging the service life of Flash. For these two points, this paper designed a new NAND Flash file system named NEOYAFFS.In aspect of the mount speed, the paper designed a super block similar to the super block function can be achieved only on the hard disk with analysing NAND Flash hardware implementation. On which stored the entire file system and file structure information, in order to reduce the the amount of data readed when mounte the file system.For wear leveling issues, this paper use a method that is similar to the UBIFS, the erased number will be stored in NAND Flash. When the file system process garbage collection, the file system will prefer to erase the blocks which has low erased number, in order to achieve the wear leveling.