NOTE
4. Distributed-System Replication
Why distributed systems keep multiple replicas of the same data, how replication improves availability and read capacity, and the major design dimensions behind replication.
This is a historical learning note and may contain outdated or incomplete understanding.
1. What Is Replication?
Replication stores copies of the same logical data on multiple nodes. Each node that stores a copy is a replica.
2. Why Replicate Data?
- improve availability and fault tolerance through redundancy;
- place data closer to users or services;
- scale read throughput by serving reads from multiple replicas.
Replication introduces a core problem: when one copy changes, the system must decide when and how other copies observe that change.