ELI5: What is Replication?
It’s like writing in two notebooks at the same time so you always have a matching copy. Replication constantly copies data to a second location so that if the first one breaks, you have an up-to-date backup ready to go.
Definition
Replication is the process of continuously or near-continuously copying data from a primary system or site to a secondary (replica) system or site, maintaining a synchronized or near-synchronized copy. Unlike traditional backups (which are point-in-time snapshots), replication provides a current or nearly current copy of data, enabling very low RPOs (near zero for synchronous replication). Replication is essential for high-availability and hot-site disaster recovery strategies.
Key Details
- Synchronous replication: writes are committed to both primary and replica simultaneously; near-zero RPO but adds write latency; typically used within the same data center or metropolitan area
- Asynchronous replication: writes are committed to primary first, then replicated to secondary with a small lag; allows greater geographic distance; small RPO gap
- Replication is not a backup substitute — it replicates corruption and ransomware encryption in real time; separate backup copies are still required
- Cloud-based replication services (AWS RDS Multi-AZ, Azure Site Recovery) are common enterprise solutions
- Exam tip: synchronous = zero data loss but latency; asynchronous = slight data loss risk but geographic flexibility
Connections
- Parent: disaster-recovery — replication is the technical mechanism for achieving low RPO in DR architectures
- See also: recovery-point-objective-rpo
- See also: 3-2-1-backup-rule