Research On Flash Memory Driver And Management Technology

JFFS2(Journaling Flash File System v2) is a kind of Log-structured file systems, it is designed specially for the embedded systems with Flash memories. Its characteristics of wear-leveling, shock-resistance make it suitable for the embedded systems.Implementation of JFFS2 in the embedded Linux system needs the support of MTD (Memory Technology Device) technology. MTD technology provides JFFS2 the abstract interface non-relevant to the memory hardware. Programming the MAPS files connects MTD and concrete flash devices. After configuring the system kernel and editing the scripts, the JFFS2 file system in Linux is achieved.The flash file systems must have garbage collection mechanism and wear-leveling mechanism for the characteristics of flash memory. The garbage collection in JFFS2 is implemented easily, but its performance is not very good in the file-accessing mode of high locality. The improved policy considers several factors that can infect the efficiency of garbage collection, such as utilization of each block, accessing frequency of data, etc. It also considers the limitation of the resources in the embedded systems.The wear-leveling mechanism needs to be modified after the garbage collection. The wear-leveling policy can be implemented in one or several function modules of the flash management. Implementing the policy in block allocation module needs to consider the relation between the rate of data refreshment and the block-erasing frequency. Meanwhile, picking the clean blocks statistically to erase of less erase time can overcome the disadvantage of implementing the policy in block allocation module separately.