臺灣博碩士論文加值系統

Android 系統由於它的免費及開放性，現今已成為最熱門的智慧型手持裝置作業系統之一。而這樣子的智慧型手持裝置還需要一個非揮發性儲存裝置，來成為它們的儲存系統，像是快閃記憶體。不同於一般的硬式磁碟機，快閃記憶體需要一個複雜的管理方式來提升它的硬體壽命。由於快閃記憶體的有區塊抹除上限的耐久度問題，在快閃記憶體上的不均勻抹除動作，終將會導致特定區塊的存取失敗，而這樣的問題將成為一個可靠的智慧型手持裝置系統的關鍵所在。在這篇研究當中，我們會去分析Android平台上的檔案系統及其資料的存取行為(包含存取權限、存取頻率及檔案類型)。根據我們所觀察到的這些特性，我們提出一個，可以辨識出哪些檔案經常被存取，而哪些不常被存取的冷熱門檔案分析器，使得基於冷熱門檔案的區塊耗損均衡演算法，可以有效的提升Android上的快閃記憶體壽命。經過我們的實驗證實，我們所提出的方法能在Android上有效的辨識出經常被寫入的檔案，並且我們的方法在效能上僅有些微的副作用。

An Android platform is widely used for mobile devices and is free open source. Usually Android-based mobile devices adopt flash-memory devices as its storage systems. Flash-memory devices are different from typical hard-disk devices and require sophisticated management to improve the lifetime and the performance. In order to establish a reliable flash-memory storage system, the flash-memory endurance problem will be an important issue. This is because flash memory could suffer from access errors due to unevenly erase operations on specific locations. In this paper, we will analyze the file system and the data accessing behaviors (includes access control, access frequency, file types) of an Android platform. According to these behaviors, we will propose a hot-cold file filter to identify hot/cold files and help evenly distributing erase operations over Android-based devices. According to the experimental results, we can demonstrate the advantages of the hot-cold file filter.

第一章 前言 1
第二章 環境背景 5
壹、 Android 快閃記憶體管理方式 5
貳、 快閃記憶體檔案系統 6
一、 JFFS/JFFS2 6
二、 YAFFS/YAFFS2 7
參、 Android 系統平台與資料儲存方式 9
第三章 相關研究與動機 12
第四章 冷熱門檔案分析器 15
壹、 檔案存取權限 15
貳、 檔案類型 17
參、 Android上的多重用戶管理 18
肆、 檔案更新頻率 20
伍、 實作方法 21
一、 系統架構 21
二、 靜態預測法 22
三、 動態辨識法 23
第五章 實驗與效能分析 29
壹、 建置實驗環境 29
貳、 實驗結果 29
一、 檔案更新頻率與熱門檔案 29
二、 檔案更新頻率機制之效能分析 37
第六章 結論 44
第七章 參考文獻 46

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[13]http://www.yaffs.net/

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