A Study On Data Management Algorithm Of Solid State Drive Flash Translation Layer

Solid State Disk(SSD)with NAND Flash memory has faster access speed,lower power consumption and better shock resistance compared with traditional hard disk.So SSD is widely used in the field of information storage.In recent years,with the continues advancement of large-scal integrated circuits and the process of manufacture technologies,the storage density of flash memory has been increasing,and Multi-Level Cell(MLC)and Trinary-Level Cell(TLC)have become mainstream NAND flash storage media.However,as storage density increases,the performance degradation and reliability issues of MLC and TLC storage are becoming more prominent.When the number of P/Es of the flash block reaches a limited number of times,the Over Provisioning space of the SSD will be replaced to ensure the security of the data in the hard disk and the capacity of the hard disk.However,the Over Provisioning space can degrade the performance of SSDs.In order to ensure the performance of SSDs,this paper mainly studies the data encoding method in the worn block and the incremental programming-based writing method in the worn block to reduce the error rate of the data in the worn block,and reuse the worn block to slow down the lifespan and performance degradation of the solid state drive.In the study of the worn block data coding method,a Coded Worn Block Management scheme is proposed in this paper.From the perspective of reducing the error rate of data in the wear block,the refresh rate of data in the wear block was reduced with this algorithm,and the life of the solid state drive was prolonged while the degradation of performance was also delayed.The CW-FTL reused the wear block to avoid the performance degradation of the SSD caused by the replacement of the Over Provisioning space after the wear block appears,and encoded the data in the wear block to ensure its data security.In the paper,the SSDSim simulator was used for simulation experiments.The wear and tear on the solid state hard disk was observed by the number of erasures and the number of garbage collections.The performance of the solid state hard disk was observed by writing the amplification factor.The experimental results showed that when the worn block occurs,the size of the Over Provisioning space of CW-FTLwas guaranteed,and the write amplification was reduced.The number of erasures of the worn block by CW-FTL was reduced by 72%,52.6%,and 63.3% in the Financialal1,Financial2,and Radius sql compared to the SR-FTL,significantly reducing wear on the worn block.In the study of incremental programming writes,the use of incremental programming and requested access characteristics to extend the potential offset time to reduce the occurrence of errors was proposed.The basic idea was that by reducing the incremental programming step size,the flash memory noise margin was increased by identifying the request access characteristics and than the cold write request was programmed into the wear block in a small step size to reduce the error of the data in the wear block.Using the SSDSim simulator for simulation experiments,by comparing the number of erasures of the SSD with the reduction of the programming step size and the number of erasures of the SSD without reducing the programming step size,the experimental results show that after reducing the programming step by half,the number of erasures of the worn block in the SSD can be reduced by up to 16.7%.