闪存存储管理算法的研究

发布时间：2018-04-13 12:01

本文选题：闪存 + 动态连续空间　；参考：《沈阳建筑大学》2013年硕士论文

【摘要】：Flash存储器由于具有体积小、重量轻、低成本、高集成度、抗震动性好等优点使得它被广泛应用于Mp3、MP4、手机等移动设备中。Flash存储器应用于嵌入式系统的最优方法就是在Flash存储器中构造一个文件系统,使得Flash存储器管理和存储文件时可以应用文件代号。由于Flash存储器中每一内存块不能无限擦写,即具有有限的寿命,每一个内存块的擦写次数的最大范围一般在105～106次之间。因此在文件存储过程中,必须采用一定的特殊机制,使得趋近于均衡使用各个内存块,避免某些块提前达到损坏,以至于影响整个Flash存储器。连续空间等概率存储算法只是将具有相同写入次数且连续的内存块定义为连续空间,这导致寻找到的连续空间并不是很大,从而影响文件的查找与读取速度。其实在庞大的数据存储过程中,系统对写入次数有一定波动范围且连续的内存块并不敏感。因此本文提出了动态连续空间等概率算法,它的主要思想是在已有的连续空间等概率存储算法的基础上加入一个动态范围,其作用是在文件存储过程中,扩大连续空间,使文件存储在更大的连续空间中,进一步解决不均衡利用存储空间的问题。在算法仿真的结果中,笔者发现加入动态范围以后,空间利用率提高了数倍。与此同时还发现此算法只专注于不断擦写的文件。其实在文件存储过程中,不仅包括不断擦写的文件,而且还包括文件存入内存块后长时间不被擦除导致所对应的内存块的写入次数非常小,从而导致闪存一部分充分利用,另一部分不被利用,从而整体上导致闪存存储空间不被均衡利用。为了解决这种闪存存储空问不均衡利用的问题,本文又提出一个基于静态数据负载均衡的存储算法,使长时间不被擦写的文件移动到经常擦写以至于写入次数很大的内存块中,保证闪存存储空间利用程度最大化,优化了Flash存储器的整体存储性能,延长了Flash存储器的使用寿命。本文在连续空间等概率存储文件管理系统的基础上设计了两种算法,并通过C++程序对算法进行了仿真。实验结果表明：在相同操作的条件下,连续空间等概率存储算法只是将具有相同写入次数且连续的内存块定义为连续空间。而笔者提出的第一个算法一动态连续空间等概率存储算法在总写入次数方面虽略逊于连续空间等概率存储算法,但是在文件平均断开次数方面明显小于连续空间等概率存储算法,提高了文件的连续性,减少了文件的查找和读取时间。笔者提出的第二个算法—基于静态数据负载平衡的存储算法,研究了将长期不移动的文件移动到写入次数较高的内存块中,避免闪存一部分由于存入长期不移动的文件而不被充分利用,另一部分被不断擦写而提前达到损坏,延长了Flash存储器的使用寿命。
[Abstract]:Flash memory has small size, light weight, low cost and high integration.The advantages of good vibration resistance make it widely used in MP4. The best method of using .Flash memory in embedded system in mobile devices such as mobile phone is to construct a file system in Flash memory.Enables Flash memory to apply file codes when managing and storing files.Because every memory block in Flash memory can not be erased indefinitely, that is, it has a limited lifetime, the maximum write number of each memory block is generally in the range of 105 ~ 10 ~ 6 times.Therefore, in the process of file storage, a certain special mechanism must be adopted to make the memory block use equably, so as to avoid the damage of some blocks in advance, and thus affect the whole Flash memory.The equal-probability storage algorithm of continuous space only defines the memory block with the same number of write times and continuous memory as continuous space, which leads to the finding of continuous space is not very large, thus affecting the speed of searching and reading files.In fact, in the huge data storage process, the system has a certain range of write times and continuous memory block is not sensitive.The problem of unbalanced utilization of storage space is further solved by making files stored in larger continuous space.In the algorithm simulation, the author found that the space utilization rate increased several times after the dynamic range was added.At the same time, it is also found that the algorithm only focuses on constantly erasing files.In fact, in the process of file storage, not only files that are constantly being erased, but also files stored in memory blocks are not erased for a long time, resulting in very small number of writes to the corresponding memory blocks, which results in the full use of a portion of flash memory.The other part is not used, so that the flash memory space is not balanced.In order to solve the problem of the unbalanced utilization of flash memory, a storage algorithm based on static data load balancing is proposed in this paper, in which files that are not erased for a long time are moved to memory blocks that are often erased and are written to a large number of times.It ensures the maximum utilization of flash memory space, optimizes the overall storage performance of Flash memory, and prolongs the service life of Flash memory.In this paper, two algorithms are designed based on the continuous space equal probability storage file management system, and the algorithm is simulated by C program.The experimental results show that under the same operation condition, the continuous space equal probability storage algorithm only defines the memory block with the same number of writes and continuous memory as continuous space.The first algorithm proposed by the author, the dynamic continuous space equal probability storage algorithm, is slightly inferior to the continuous space equal probability storage algorithm in terms of the total write times.However, the average number of disconnected files is obviously smaller than the probability storage algorithm such as continuous space, which improves the continuity of files and reduces the searching and reading time of files.Based on the static data load balancing storage algorithm, the second algorithm proposed by the author is to move the long-immovable files to the memory blocks with high write times.One part of the flash memory is not fully utilized because it is stored in the long-immovable files, and the other part is continuously erased and damaged in advance, thus prolonging the service life of the Flash memory.
【学位授予单位】：沈阳建筑大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TP333

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