---
title: "Replication"
description: "Replication copies data across servers in near real time. Learn master-slave and master-master topologies plus synchronous and asynchronous modes."
url: "https://nodea.io/en/glossary/replication"
lang: "en"
updated: "2026-07-13"
---

# Replication

> Replication is the process of automatically copying and synchronising data across multiple servers so that the same information is available in more than one place.

**Replication** is the process of automatically copying and synchronising data across multiple servers so the same information exists in more than one place. It is most often discussed in the context of [databases](https://nodea.io/en/glossary/database), but files, objects in a storage system and entire file systems can be replicated too. The goals are higher [availability](https://nodea.io/en/glossary/high-availability), load distribution, and keeping data geographically closer to users in different regions.

## How replication works

A source server (the master or primary) records every change in a transaction log, and target servers (slaves or replicas) read that log and replay the same operations on themselves. This keeps replicas a faithful mirror of the source. There are two main modes:

- **asynchronous replication** — the source acknowledges a write immediately and replicas catch up with a slight lag; fast, but risks losing the most recent transactions in a sudden failure,
- **synchronous replication** — a write is confirmed only after it is durable on the replicas; safer, but slower.

In terms of topology you will meet the **master-slave** model (one writer, many readers) and **master-master**, where several nodes accept writes at the cost of complex conflict handling.

## Replication in practice

Replication underpins high-availability architectures: if the primary node fails, traffic switches to a replica (failover) and the service keeps running. It also scales reads — *SELECT* queries are spread across replicas to offload the writer, a pattern used by high-traffic stores and portals. Engines such as [MariaDB](https://nodea.io/en/glossary/mariadb) and [MySQL](https://nodea.io/en/glossary/mysql) provide replication natively. Remember that a replica is not a backup — it faithfully copies bad operations as well, so full protection comes only from combining replication with regular backups.

### How is replication different from a backup?

Replication keeps a live, current copy of data on another server for availability and read scaling. A backup is a point-in-time snapshot that protects against mistakes or deletion. Because replication instantly copies errors too, it is not a substitute for backups.

### Does synchronous replication slow down the database?

It can, because a write is only acknowledged once it has been stored on every node, adding network latency. In return it guarantees that no committed transaction is lost after a failure, which is critical for financial and other high-integrity systems.

## Related

- [Database](https://nodea.io/en/glossary/database)
- [MariaDB](https://nodea.io/en/glossary/mariadb)
- [MySQL](https://nodea.io/en/glossary/mysql)
- [High availability (HA)](https://nodea.io/en/glossary/high-availability)
- [Backup](https://nodea.io/en/glossary/backup)

---

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