臺灣博碩士論文加值系統

由於近年來大眾對於電腦科學之資料安全議題的關注以及重視，傳統資料刪除指令的能力已不符合現今儲存系統上對於資料安全的需求。因此，新興之資料淨化技術以及擦洗式指令皆被提出，以符合將機密資料完全徹底地從儲存裝置中移除乾淨的需求。然而，資料淨化的過程有可能導致大量的資料搬移而造成時間和空間上的浪費，並且擦洗式指令也會造成資料干擾之議題。此篇論文中，我們目標為同時利用資料淨化和擦洗式指令的優點，以提出一個基於三維快閃記憶體上有效率之新興資料刪除技術。不同於以往的研究中採取加密式或者傳統刪除式的方法以達成資料淨化之目的，此篇論文同時利用擦洗式指令的干擾議題以及三維快閃記憶體的特性，而進一步提昇資料淨化之效能。此外，我們也提出了一個以群集為基礎的資料寫入策略，因此減少資料搬移的負擔且有效地利用資料干擾之特性，而使得資料淨化技術之效率提昇。上述設計架構之能力經由一連串的實驗及驗證，我們亦得到令人激賞之結果。

Because of the increasing concern of data security, the ability of traditional erase and deletion commands can no longer support such a security requirement of today’s storage systems. As a result, the ideas of sanitization and scrubbing operations are proposed to meet the needs of clearly and completely removing the sensitive data from the storage devices physically. However, the sanitization process can result in the significant overhead of live-page-copying, and the scrubbing can result in the disturbance issues. In this work, we aim at exploring a way to take advantage of benefits of both sanitization and scrubbing operations to propose an efficient sanitization design for 3D NAND flash memory. Different from the past work which adopted encryption-based and erase-based schemes to achieve the goal of data sanitization, this paper exploiting the considerations of scrubbing disturbances and characteristics of 3D flash memory (e.g., programming latency and page layout) to improve the performance of sanitization. In addition, a grouping-based write strategy is proposed to not only reduce the live-page-copying overheads but also exploit the disturbance property to improve sanitization efficiency. The capability of the proposed design is evaluated by a series of experiments, for which we have very encouraging results.

Abstract in Chinese iii
Abstract v
Contents vii
List of Figures ix
List of Tables x

1 Introduction 1
1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Architecture of 3D NAND Flash . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Related Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.4 Objectives and Contributions . . . . . . . . . . . . . . . . . . . . . . . . 4
1.5 Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2 Background and Research Motivation 6
2.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.2 Sanitization on HDDs and SSDs . . . . . . . . . . . . . . . . . . . . . . 7
2.3 Scrubbing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.4 Summary of Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3 Scrubbing-aware Sanitization Design 12
3.1 Design Concept: Sanitization Overhead . . . . . . . . . . . . . . . . . . 12
3.2 Design Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.3 Grouping-basedWrite Strategy . . . . . . . . . . . . . . . . . . . . . . . 19
3.4 Reliable Grouping-basedWrite Strategy . . . . . . . . . . . . . . . . . . 22
3.5 Disturbance Infection Scrubbing Policy . . . . . . . . . . . . . . . . . . 24
3.6 Garbage Collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

4 Performance Evaluation 31
4.1 Evaluation Metrics and Experiment Setup . . . . . . . . . . . . . . . . . 31
4.2 Experiment Result . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

5 Concluding Remarks 37
5.1 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

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