Redo Log vs Binlog: 4 Key Differences Every MySQL Engineer Should Know

Redo log and binlog are important components of MySQL; this article details four major differences between them.

1. Purpose Difference

Redo Log (重做日志)： Mainly ensures data durability and consistency by recording changes of committed transactions, allowing recovery to a consistent state after a crash.

Binlog (二进制日志)： Primarily used for data replication, recovery, auditing, analysis, and enabling high‑availability features such as master‑slave replication.

2. Recorded Content Difference

Redo Log： Records the actual changes of committed transactions, such as INSERT, UPDATE, DELETE, and related page updates.

Binlog： Records all database changes, including data modifications and DDL statements like CREATE TABLE, ALTER TABLE, as well as other management operations.

3. Content Type Difference

Redo Log： Contains before‑and‑after data for replaying committed transaction changes.

Binlog： Contains the SQL statements or binary data needed to reconstruct the database changes.

4. Lifecycle Difference

Redo Log： Typically written in a circular fashion; old records are overwritten because its purpose is immediate recovery, not long‑term storage.

Binlog： Usually retained for a configurable period to support replication, recovery, auditing, and analysis, so its lifecycle is longer.

In summary, redo logs focus on ensuring data durability and consistency, while binlogs support a broader range of applications such as replication, recovery, auditing, analysis, and high‑availability.