95 lines
7.9 KiB
XML
95 lines
7.9 KiB
XML
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<title id="diagram-title">fsync() 의 요구가 물리 storage 까지 내려가는 사슬</title>
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<desc id="diagram-description">위에서 아래로 읽는다. 맨 위 PostgreSQL 이 fsync() 를 부르고 그 요구가 Guest Filesystem 으로 내려간다. Guest Block Layer 에서 FLUSH 등의 요청으로 바뀌고, virtio-blk 를 지나 VM 경계를 넘어 QEMU / Backend 로 간다. 거기서 Host Storage Stack 을 지나 맨 아래 Physical Storage 까지 그 의미가 전달되어야 완료가 성립한다. 여섯 번 손이 바뀌는 동안 한 곳이라도 그 의미를 지키지 않으면 게스트가 받은 완료 응답이 거짓이 된다. write() 완료와 writeback 완료, fsync/flush 완료, 전원 장애에도 안전한 durability 가 서로 다르다는 구분은 본문의 코드블록이 맡는다.</desc>
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