# 【etcd】WAL 与快照：预写日志、crash recovery 与 commit vs applied

DevFeed: [【etcd】WAL 与快照：预写日志、crash recovery 与 commit vs applied](<https://devfeed.tech/articles/etcd-wal-crash-recovery-commit-vs-applied-33985.md>)

Original publisher: [Read original article](<https://quant67.com/post/etcd/03-wal-snapshot/03-wal-snapshot.html>)

Author: Liao Tonglang

Published: 2026-08-26T00:00:00Z

Content type: tutorial

Language: zh

Sources: [土法炼钢 - 系统与基础设施](<https://devfeed.tech/sources/source-4.md>)

Topics: [etcd](<https://devfeed.tech/topics/etcd.md>), [Raft](<https://devfeed.tech/topics/raft.md>), [Kubernetes](<https://devfeed.tech/topics/kubernetes.md>)

Tags: [applied-index](<https://devfeed.tech/tags/applied-index.md>), [committed-index](<https://devfeed.tech/tags/committed-index.md>), [crash-recovery](<https://devfeed.tech/tags/crash-recovery.md>), [distributed](<https://devfeed.tech/tags/distributed.md>), [etcd](<https://devfeed.tech/tags/etcd.md>), [kubernetes](<https://devfeed.tech/tags/kubernetes.md>), [latency](<https://devfeed.tech/tags/latency.md>), [persistence](<https://devfeed.tech/tags/persistence.md>), [safety](<https://devfeed.tech/tags/safety.md>), [snapshot](<https://devfeed.tech/tags/snapshot.md>), [v3-5-33](<https://devfeed.tech/tags/v3-5-33.md>), [wal](<https://devfeed.tech/tags/wal.md>)

## AI overview

This tutorial explains how etcd v3.5.33 uses WAL segments and Raft snapshots for persistence, log compaction, and crash recovery. It also describes how committed and applied indexes can diverge, causing Watch delays or extended not-ready periods even when Raft replication appears healthy.

## Source excerpt

拆解 etcd v3.5.33 的 WAL 段文件、Raft snapshot 触发与重启 recovery 顺序；钉清 committed index 与 applied index 分叉对排障与 K8s 控制面的含义。