增強快閃儲存記憶體壽命的動態sector重新映對機制

Abstract

近年在NAND Flash技術的急速發展，無論在容量上、穩定度，都有長足的進步，逐漸成為Embedded System上儲存裝置的主要原件，然而NAND Flash發展至今，仍存在著wear-out的情況，因其都有一個磨損的極限，因此，平均磨損(wear-leveling)演算法便十分的重要。為了使其壽命延長，因此發展出各種wear-leveling的演算法，期望透過平均磨損機制，提高NAND Flash的使用壽命。由於一般 wear-leveling必須跟 disk emulation (FAL or FTL) 緊密結合，在出產時便已經內建在 block device emulation, 一般來講可能是不能修改的 driver 或者是已經是SSD firmware。本論文使用Windows CE平台，在此架構下，提出一個稱之為RLFAL的檔案系統架構，透過本論文所提出之RLFAL，可以在不更動原始FAL及廠商所提供的NAND Flash Device Driver的前提下，使原有系統上具備wear-leveling機制，並可適用於市面上各廠商所開發之NAND flash。本論文與RLFAL架構中實作的平均磨損演算法(wear-leveling)包括透過LRU、FIFO queue機制，協助hot、cold data的remap機制。透過本論文所提出的RLFAL檔案系統架構不但可以不須更動source code，又可使原有NAND flash檔案系統具備更好wear-leveling的效果。實驗證明，使用RLFAL的系統與原本的FAL相比較，其wear-leveling的效果遠高於原本的FAL。

As the flash technology dramatically develop, improving the capacity and stability of flash memory. Now flash memory is the key component of embedded system storage system. However the wear-out situation caused by the lifetime is still the major problem of flash memory. Wear-leveling algorithm is important for every flash system design. For extend the flash memory lifetime, there are many related work proposed. By these algorithms, it can improve the flash memory lifetime. WinCE is current main stream platform on the marketing. However it has higher software authorize cost is known. This thesis focus on the problem of WinCE software authorize cost. We propose a file system architecture called RLFAL. By using RLFAL make it possible to improve the wear-leveling effect on the original WinCE platform without modifying any original flash related architecture. RLFAL is consistent of three main part, LRU table, FIFO Queue and remap policy. By simulation we improve that RLFAL can reduce the develop cost, and improving the wear-leveling effect of original platform.