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研究生：	許勝杰 Syu, Sheng-Jie
論文名稱：	快閃記憶體儲存管理系統之設計與實作 Design and Implementation of a Flash Storage System
指導教授：	陳　敬 Chen, Jing
學位類別：	碩士 Master
系所名稱：	電機資訊學院 - 電機工程學系 Department of Electrical Engineering
論文出版年：	2004
畢業學年度：	92
語文別：	中文
論文頁數：	54
中文關鍵詞：	快閃記憶體、儲存系統、嵌入式系統
外文關鍵詞：	Storage System, Flash Memory, Embedded systems, Garbage Collection
相關次數：	點閱：86 下載：3
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　　快閃記憶體有著體積小、重量輕、防震、低耗電、不具揮發性、高效能等優點，相當適合作為行動式手持設備與嵌入式系統等環境之資料儲存媒體。但由於快閃記憶體無法原地更新資料的特性且區塊抹除次數有限制，以快閃記憶體為儲存媒體之檔案系統設計時必須考慮這些限制因素。本論文提出一個以註冊為基礎之冷熱資料辨識法(Register Based Hot-Cold Data Identification)與使用三個管理策略，分別為：資料放置策略(Data Placement Policy)、可用空間分配策略(Free Space Allocation Policy)與無效空間回收策略(Recycle Policy)，能有效地將回收快閃記憶體無效空間時之系統負荷降低，同時也能較均衡地抹除快閃記憶體區塊，延長快閃記憶體的使用壽命。此外，本論文亦提出一主動式回收快閃記憶體無效空間之機制，模擬實驗結果顯示，與使用被動回收方法比較，此一主動回收快閃記憶體無效空間之機制的確能有效地減少讀寫動作因區塊回收動作所造成的時間延遲。

　　Flash memory has the advantages of small size, lightweight, shock resistant, no mechanical delay involved, high performance and low power consumption. Thus it shows promise for being used in storage devices for consumer electronics, embedded systems and mobile computers. However, flash memory bears restrictions of data erase-before-write and limited block erased counts. Designing a filesystem for flash memory has to take into account these issues and to adopt effective solutions. In this thesis, we propose a RB (register based) hot-cold data identification method and three flash management policies to reduce the system overhead caused by operations of recycling invalid space, and to evenly use all blocks in flash memory chip. We also propose an active garbage recycling mechanism which periodically recycles invalid space in flash memory. Experiment results show that system using the active recycling approach has excellent performance over systems using passive recycling approach after handled serials of requests.

第一章 簡  介 ............................................................................................ 1
1 背景知識 ............................................................................................. 1
2 研究動機 ............................................................................................. 4
3 論文組織 ............................................................................................. 5
第二章 相關研究 ...................................................................................... 6
1 快閃記憶體管理系統架構	 ................................................................ 6
2 無效空間回收演算法與使區塊抹除次數平均之考量 ..................... 8
3 冷門資料與熱門資料辨別方法 ....................................................... 10
4 快閃記憶體管理系統記憶體需求考量 ........................................... 11
5 無效空間回收之時機與回收量大小 ............................................... 12
第三章 快閃記憶體管理系統之設計 .................................................... 13
1 系統架構 ........................................................................................... 13
2 快閃記憶體管理策略 ....................................................................... 16
2.1 資料放置策略 (Data Placement Policy) .......................................... 16
2.2 可用空間分配策略 (Free Space Allocation Policy) ........................ 17
2.3 無效空間回收策略 (Invalid Space Recycling Policy) .................... 18
2.4 熱門資料與冷門資料之鑑別 (Hot-Cold Data Identification) ........ 20
3 系統實作 ........................................................................................... 22
3.1 寫入單位管理結構 ........................................................................ 22
3.2 區塊管理結構 ................................................................................ 23
3.3 邏輯-實體位址對照表 (Address Translation Table) ...................... 24
3.4 快閃記憶體空間之管理與維護 .................................................... 24
3.4.1 使用中區塊變為無效區塊之流程 ............................................. 25
3.4.2 無效區塊變為可用區塊之流程 ................................................. 26
3.5 管理策略之使用 ............................................................................ 28
4 實驗結果與分析 ............................................................................... 30
4.1 實驗環境 ........................................................................................ 30
4.2 冷熱資料判別法比較 .................................................................... 32
4.3 回收演算法效率比較 .................................................................... 33
4.4 區塊抹除次數平均狀況比較 ........................................................ 35
4.5 記憶體需求討論 ............................................................................ 37
5 結論 ................................................................................................... 38
第四章 主動回收快閃記憶體無效空間機制 ........................................ 40
1 系統模型 ........................................................................................... 40
2 系統任務 ........................................................................................... 41
2.1 系統管理任務 (System Manager Task) .......................................... 41
2.2 無效空間收集任務 (Collector Task) .............................................. 44
2.3 區塊抹除任務 (Eraser Task) ........................................................... 45
2.4 讀寫處理任務 (Read/Write Handler Tasks)	.................................... 45
3 實驗結果分析 ................................................................................... 46
4 結論 ................................................................................................... 49
第五章 總結與未來研究方向 ................................................................ 51
1 總結 ................................................................................................... 51
2 未來研究方向 ................................................................................... 51
參考文獻 ................................................................................................. 53


                                    

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校外：2004-07-20公開

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