Optimization Of Large Flash Page Access Based On Reprogramming

With the advance in flash memory manufacturing process, NAND flash memory chips have higher storage density, forming increasingly large-capacity SSDs(SSD). As the basic read and write unit of flash memory, flash page size is also increasing. On the one hand, due to the effect of manufacturing process, the flash memory chips sacrifice lifetime for storage density, while increase write delay. On the other hand, with the problem of mismatch between file system block and flash page size, large-capacity flash memory pages result in a waste of time of data transfer and storage space.Existing Flash Translation Layer(FTL) manages storage space in granularity of flash page or flash block, which can not solve the performance problem of large-capacity flash pages. By using rewritable property of flash memory, a flash page can be programmed repeatedly without erasing operation. Based on this feature, we designed Mapping Granularity Adaptive Flash Translation Layer(MGA-FTL), adopting a smaller granularity for flash storage space management, enabling allocation and address mapping aiming at partial space within flash page, and supporting multiple small update operations on the same flash page, which thus improves the efficiency of large-capacity flash pages. Moreover, we designed an approach to reduce flash page data transmission overhead by filling the data in the device directly. The scheme design was implemented and tested on SSD simulator, and the results show that the program effectively improves the read and write performance of large-capacity flash pages, reduces the number of write amplification and erase operations to solid state disk, and extends lifetime of SSDs.