臺灣博碩士論文加值系統

SSD全名為Solid-state drive，是基於NAND-Flash做為永久儲存裝置。NAND-Flash具有容量較大，改寫速度快等優點，近年來隨著NAND快閃記憶體的成本降低，SSD固態硬碟的應用範圍也就跟著增加。相較於傳統硬碟，SSD有隨機存取的速度很快、且存取時間固定、體積小等優點，但相對也有損壞時資料不可挽救、Cell讀寫次數有限制的缺點。
　　為了管理這些限制，SSD會有一個FTL（Flash Translation Layer）來管理Cell下次要寫到哪個地方，避免一直寫到同個地方以延長Cell的壽命，稱為Wear Leveling。然而為了更好的資料回收，Trim告訴SSD哪些資料為無效的資料，並適時刪除，可以用來提升GC（Garbage Collection）效率。然而Trim在過去只被用來做GC效率的提升，較少的研究將它作為資料配置的依據。因此本篇論文提出了選擇write pointer機制來透過Trim資訊的方式進行資料配置，從源頭增進GC效率。

The full name of SSD is Solid-state drive, is a computer storage device. NAND-Flash storage is a type of flash storage, it has the advantage of large capacity and high read/write performance. NAND memory can still store data when powering off, but DRAM not. In recent years, the application with SSD will increase.
To manage these limits, SSD uses FTL to manage which location the Cell should write to, avoid writing to the same location all the time to prolong the life of the Cell, called Wear Leveling. However, to better the data recovery, Trim will tell SSD which data is invalid data, and delete in due time, it can be used to improve GC efficiency. Trim is used to only improve GC efficiency, few studies use it to data allocation. Thus, this paper proposes to select the write pointer mechanism to allocate data by Trim, to improve GC efficiency from the source.

中文摘要　．．．．．．．．．．．．．．．．．．．．．．．．．．．．．　i
ABSTRACT　．．．．．．．．．．．．．．．．．．．．．．．．．．．　ii
誌謝　．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．　iii
目錄　．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．　iv
表目錄　．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．　vi
圖目錄　．．．．．．．．．．．．．．．．．．．．．．．．．．．．．　vii
程式碼目錄　．．．．．．．．．．．．．．．．．．．．．．．．．．．．　viii
第一章 緒論　．．．．．．．．．．．．．．．．．．．．．．．．．．． 1
1.1 研究背景與動機　．．．．．．．．．．．．．．．．．．．． 1
1.2 研究目標　．．．．．．．．．．．．．．．．．．．．．．． 2
1.3 論文組織架構　．．．．．．．．．．．．．．．．．．．．． 3
第二章 背景知識　．．．．．．．．．．．．．．．．．．．．．．．．． 4
2.1 NAND Flash　．．．．．．．．．．．．．．．．．．．．．． 4
2.1.1 NAND Flash的種類．．．．．．．．．．．．．．． 4
2.1.2 NAND Flash特性．．．．．．．．．．．．．．． 4
2.2 SSD　．．．．．．．．．．．．．．．．．．．．．．．．． 5
2.2.1 Flash Translation Layer　．．．．．．．．．．．．． 7
2.2.2 Mapping Table　．．．．．．．．．．．．．．．． 8
2.2.3 Trim Command　．．．．．．．．．．．．．．．． 8
2.2.4 Garbage Collection　．．．．．．．．．．．．．． 9
2.2.5 Write Pointer　．．．．．．．．．．．．．．．．． 12
2.2.6 Line　．．．．．．．．．．．．．．．．．．．． 13
2.3 QEMU　．．．．．．．．．．．．．．．．．．．．．．．． 14
2.4 FEMU　．．．．．．．．．．．．．．．．．．．．．．．． 15
第三章 SSD的設計與延伸　．．．．．．．．．．．．．．．．．．．． 16
3.1 SSD的設計　．．．．．．．．．．．．．．．．．．．．． 16
3.2 Trim Table　．．．．．．．．．．．．．．．．．．．．．． 16
3.3 修改Write Pointer　．．．．．．．．．．．．．．．．．．． 17
3.3.1 兩個Write Pointer　．．．．．．．．．．．．．． 17
3.3.2 Write Pointer的選擇機制　．．．．．．．．．．． 18
3.3.3 Page Allocate　．．．．．．．．．．．．．．．． 19
第四章 SSD的延伸實驗　．．．．．．．．．．．．．．．．．．．．． 23
4.1 實驗工具介紹－FIO．．．．．．．．．．．．．．．．．．． 23
4.2 實驗結果．．．．．．．．．．．．．．．．．．．．．．． 23
第五章 結論　．．．．．．．．．．．．．．．．．．．．．．．．．． 27
5.1 結論　．．．．．．．．．．．．．．．．．．．．．．．． 27
5.2 未來展望　．．．．．．．．．．．．．．．．．．．．．． 28
參考文獻　．．．．．．．．．．．．．．．．．．．．．．．．．．．．．29

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