基于非均衡通道的NAND Flash混合存储技术研究

发布时间：2018-03-26 02:03

本文选题：NAND　切入点：Flash　出处：《国防科学技术大学》2012年硕士论文

【摘要】：NAND Flash容量的增长和其性能及可靠性之间存在着矛盾。单颗NAND Flash的容量不断增大的同时，其基本单元——块和页的容量也在随之增大，但是文件系统访问SSD时的基本单位——扇区没有变。一个物理页包含的逻辑扇区数越来越多，并且页具有先擦再写的特性，写入的最小单位是一个页，擦除的最小单位是一个块，故重写入问题越来越严重，需要探索更有效的架构和管理算法来提高存储的性能。并且，随着容量的增大，NAND Flash制程进一步降低，致使NANDFlash存储单元总的擦写次数不断降低，需要更加充分利用有限的擦写次数来提高存储系统的可靠性。此外，数据量的骤增对SSD的容量提出了新的要求，现有NAND Flash存储组织架构已经不能适应容量增长的要求。针对当前NAND Flash容量和性能之间，，以及物理块/页大小与扇区大小之间存在的矛盾，设计了一种非均衡的NAND Flash存储组织架构，包括非均衡通道和混合NAND Flash。非均衡通道将几个物理通道合并形成超级通道，使NAND Flash的“物理存储单元”进一步增大，从而降低地址映射表的规模，减小RAM资源的消耗。混合NAND Flash通过将MLC和SLC混合使用，充分利用SLC的性能和可靠性优势以及MLC的价格和容量优势来提高系统容量，同时保证系统性能。基于提出的非均衡架构，还设计了基于块组的地址映射算法、通道数据滤波器以及请求队列的调度优化算法。在DiskSim和SSD Model的基础上，设计了非均衡NAND Flash架构下的SSD性能和可靠性仿真平台。在指定的性能和可靠性评估条件下，映射表减小了25%到50%，RAM资源占用最小约为BAT的十分之一；随机数据读写性能方面，提出的非均衡组织架构以25%的SLC比例达到将近100%SLC系统的性能，顺序读写速度介于全SLC和全MLC之间，增幅不大；可靠性能相对全MLC系统大幅提升。
[Abstract]:There is a contradiction between the growth of NAND Flash capacity and its performance and reliability. As the capacity of a single NAND Flash increases, so does the capacity of its basic unit, blocks and pages. But the basic unit of file system access to SSD-the sector remains the same. A physical page contains more and more logical sectors, and the page has the feature of erasing before writing, the smallest unit of writing is a page, and the smallest unit of erasure is a block. Therefore, the problem of rewriting is becoming more and more serious, so it is necessary to explore more effective architecture and management algorithms to improve storage performance. It is necessary to make full use of the limited erasing times to improve the reliability of the storage system. In addition, the sudden increase in the amount of data puts forward new requirements for the capacity of SSD, and the existing NAND Flash storage organization can no longer meet the requirements of capacity growth. Aiming at the contradiction between current NAND Flash capacity and performance, and between physical block / page size and sector size, an unbalanced NAND Flash storage organization architecture is designed. Including unbalanced channels and mixed NAND Flash. Unbalanced channels combine several physical channels to form superchannels, further increasing the "physical storage unit" of NAND Flash, thus reducing the size of address mapping tables. To reduce the consumption of RAM resources, hybrid NAND Flash improves system capacity by mixing MLC and SLC, making full use of the performance and reliability advantages of SLC and the price and capacity advantages of MLC, while ensuring system performance. The address mapping algorithm based on block group, channel data filter and scheduling optimization algorithm of request queue are also designed. On the basis of DiskSim and SSD Model, the simulation platform of SSD performance and reliability under unbalanced NAND Flash architecture is designed. Under the specified performance and reliability evaluation conditions, the mapping table reduces the minimum resource consumption of BAT by 25% to 50% of BAT. In the aspect of reading and writing performance of random data, the proposed disequilibrium organization architecture achieves the performance of nearly 100%SLC system by 25% SLC, the speed of sequential reading and writing is between full SLC and full MLC, the increase is not large, and the reliability performance is greatly improved compared with the whole MLC system.
【学位授予单位】：国防科学技术大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TP333

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