Disaster Recovery Concepts
Disaster recovery concepts
What you will learn
- Distinguish RTO (recovery time objective) from RPO (recovery point objective).
- Recall the three backup recovery site types: hot, warm, and cold.
- Explain why site type choice ties directly to cost and recovery speed.
- Choose the right site type for a given scenario based on downtime sensitivity.
Disaster recovery (DR) answers a different question than high availability: not "what if one component fails?" but "what if the entire site is lost — fire, flood, a complete data center failure?" The answer starts with two clear numbers: how much downtime is tolerable, and how much data loss is tolerable.
RTO vs. RPO
| RTO (Recovery Time Objective) | RPO (Recovery Point Objective) | |
|---|---|---|
| Measures | Maximum acceptable downtime | Maximum acceptable amount of data loss |
| The question | "How long can we be down?" | "Which earlier backup do we fall back to?" |
| What drives it | The recovery site's speed and readiness | How frequently backups are taken |
Recovery site types
| Hot Site | A fully ready, continuously synchronized site — recovery in minutes, highest cost. |
|---|---|
| Warm Site | A site with ready hardware but data not synchronized in real time — recovery in hours, moderate cost. |
| Cold Site | Just a physical space without ready hardware or current data — recovery in days, lowest cost. |
Memory aid
RTO = Time, RPO = Point (in time to fall back to). And the faster the required site (hot faster than warm faster than cold), the higher its cost — there's no universally "best" site, only the one matching the acceptable downtime sensitivity.
Quick check
Answer in your head first, then reveal.
What's the fundamental difference between RTO and RPO?Reveal the answer
RTO measures maximum acceptable downtime; RPO measures maximum acceptable data loss.
Which recovery site type is fastest but costs the most?Reveal the answer
Hot site.
Why does a cold site mean recovery in days, not minutes?Reveal the answer
Because it's just a physical space without pre-ready hardware or current data — all of it needs to be set up from scratch.
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Sources
Used to verify the facts. The writing is original to Passuit.