Every extra nine costs 10× more and forgives 10× less. Learn what availability targets actually mean, why redundancy is non-negotiable, and how to build backups you can restore from — before you need them.
"We're up 99% of the time" sounds great — until you realize that's over three and a half days of outage per year. Here's what each availability class actually permits.
| Availability | Nickname | Downtime / year | Downtime / month | Downtime / week |
|---|---|---|---|---|
| 90% | One nine | 36.5 days | 73 hours | 16.8 hours |
| 99% | Two nines | 3.65 days | 7.3 hours | 1.68 hours |
| 99.9% | Three nines | 8.77 hours | 43.8 minutes | 10.1 minutes |
| 99.99% | Four nines | 52.6 minutes | 4.38 minutes | 1.01 minutes |
| 99.999%★ five nines | Five nines | 5.26 minutes | 26.3 seconds | 6.05 seconds |
| 99.9999% | Six nines | 31.6 seconds | 2.63 seconds | 0.6 seconds |
Drag the slider to see how much downtime a given availability target actually allows.
Hardware fails, networks partition, data centers lose power. High availability isn't about preventing failure — it's about making failure boring. Every component your service depends on should have an answer to the question: "what happens when this dies?"
Run at least one more instance than you need. N+1 survives a single failure; N+2 survives a failure during maintenance. Load balancers spread traffic and route around dead nodes automatically.
A second server in the same rack shares the same power feed, switch, and flood plain. Real resilience means multiple availability zones — ideally multiple regions — with automated failover.
Dual power supplies, RAID storage, bonded NICs, multiple upstream providers, secondary DNS. The unglamorous layers are the ones that take you down at 3 a.m.
Untested failover is a rumor, not a capability. Practice killing nodes on purpose (chaos engineering) so the first real failure isn't also the first rehearsal.
Redundancy protects you from hardware failure. It does nothing against ransomware, accidental deletion, or a bad migration — replicas happily replicate your mistakes. That's what backups are for.
The production copy plus at least two backups. One backup is zero backups the day it turns out corrupted.
Don't keep every copy on the same storage system or provider. Diversity limits the blast radius of any single failure.
At least one copy in a different physical location — and ideally offline or immutable, where ransomware can't reach it.
Nobody actually wants backups — they want restores. Schedule regular test restores to a clean environment and time them. If you've never restored it, you don't have a backup; you have hope.
Knowing the theory is the easy part. If your business can't afford downtime, the consultants at Triton design, harden, and monitor infrastructure for a living — availability audits, redundancy architecture, backup & disaster-recovery drills, and 3 a.m. incident response.
Tell us your uptime target. We'll tell you what it takes to get there — starting with a free uptime audit, no strings attached.
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