목차

Ⅰ. 서론 ·············································································································· 1
Ⅱ. 선행연구 ······································································································ 3
2.1 IoT ··············································································································· 3
2.2 플래시 메모리 ··························································································· 4
2.2.1 NAND 플래시 메모리 ······································································· 4
2.2.2 플래시 메모리 구조 ············································································ 5
2.2.3 플래시 메모리 특징 ············································································ 6
2.3 단편화(Fragementation)와 플래시 메모리 ···········································8
2.3.1 단편화 ···································································································· 8
2.3.2 단편화가 플래시 메모리에 끼치는 영향 ········································ 9
2.4 FAT 파일시스템 ·····················································································10
2.4.1 부트 레코드(Boot Record) 영역 ·····················································10
2.4.2 예약된(Resrved) 영역 ·······································································11
2.4.3 FAT(File Allocation Table) 영역 ···················································11
2.4.4 데이터(Data) 영역 (파일과 디렉터리) ·········································· 12
Ⅲ. 연구 동기 ··································································································13
3.1 단편화에 의한 성능 분석 실험 ···························································13
3.2 IoT 디바이스의 센서 데이터 특징과 저장 방식 문제점 ··············· 15
3.3 IoT 디바이스의 갑작스런 전원 차단 및 스토리지 분리 문제 ····· 17
3.4 빈번한 메타데이터 업데이트 문제 ·····················································17
3.5 기존 IoT 디바이스를 위한 파일시스템 문제 ··································· 18
Ⅳ. 문제 해결을 위한 기법 및 정책 ························································ 19
4.1 센서 데이터별 파티셔닝 기법 ·····························································19
4.2 미리할당(Pre-Allocation) 정책 ·····························································20
4.3 기존 파티셔닝과 미리할당 문제점 ·····················································22
Ⅴ. 설계 및 구현 ······························································································24
5.1 유닛(unit)기반 파티셔닝과 미리할당 ·················································24
5.1.1 고정된 위치를 갖는 유닛(unit)의 필요성 ···································· 23
5.1.2 파티셔닝을 위한 자료구조 ······························································25
5.1.3 미리할당 정책과 PA 유닛을 위한 자료구조와 장점 ·················26
5.2 Internal Checker ·····················································································28
5.2.1 fsck 유틸리티와 호환성···································································28
5.2.2 구체적 충돌 현상 ··············································································28
5.2.3 Internal Checker 메커니즘 ····························································30
5.3 SD카드 전원 결함 및 제거 문제 해결 메커니즘 ····························31
5.3.1 미리할당 정책과 Sync를 통한 동기화의 한계 ····························31
5.3.2 재부팅 후 제어 자료구조 복원 ······················································32
5.4 IoT 디바이스 워크로드 합성 생성기와 매니저 ······························· 33
Ⅵ. 평가 ··············································································································35
6.1 실험환경 ···································································································35
6.2 실험 내용 및 결과 ·················································································36
6.2.1 센서 이벤트별 파티셔닝 정책 검증 ··············································36
6.2.2 메타데이터 업데이트 비교 실험 ····················································37
6.2.3 블록 I/O 요청 횟수 비교 실험 ·····················································38
6.2.4 센서 데이터 파일에 대한 단편화 측정 ········································ 39
6.2.5 Fsck에 의한 중간 삽입된 EOF 확인 ············································ 40
6.2.6 Space Leak 발생 확인 ·····································································41
6.2.7 Internal Checker에 의한 삽입된 EOF 제거 및 복구 ················ 42
6.2.8 Internal Checker에 의한 Space Leak 제거 ·································43
Ⅶ. 결론 ··············································································································44
참고문헌 ·············································································································45
영문요약 ·············································································································49