> For the complete documentation index, see [llms.txt](https://gunkim.gitbook.io/undefined/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://gunkim.gitbook.io/undefined/lsm-tree.md).

# lsm-tree

### 배운 개념

* 단순한 "파일 쓰기"가 아니라 디스크 헤더를 움직이지 않는 \*\*순차 I/O(Append-only)\*\*라는 본질적 하드웨어 메커니즘을 기반으로 함.
* 인덱스가 없는 것이 아님. 메모리의 MemTable과 디스크의 SSTable(희소 인덱스)을 통해 검색을 지원하지만, 여러 테이블을 뒤져야 해서 읽기 성능은 B 트리보다 느림.

### 오답 및 정정

> \[!WARNING] **오개념**: LSM 트리는 쓰기에만 집중하고 인덱스가 아예 없다. **정정**: MemTable과 희소 인덱스를 엄연히 가지며, 단지 여러 파편화된 SSTable을 찾아봐야 하기 때문에 B 트리 대비 읽기가 느린 것임.

### 복습 체크

* [ ] LSM 트리가 B 트리보다 쓰기 속도가 빠른 근본적인 디스크 I/O 레벨의 이유는 무엇인가?
* [ ] MemTable과 SSTable의 역할은 각각 무엇인가?

\[\[b-tree]] \[\[compaction-strategies]] \[\[bloom-filter]]


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