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可用性与 SLA 计算器.
把可用性百分比换算为允许的停机时间，并根据组件和冗余估算整个系统的可用性。
CALCULATED IN YOUR BROWSER · NOTHING IS UPLOADED
Allowed downtime per year8.8 h99.9 %
- Allowed downtime per month
- 43.8 min
- Allowed downtime per year
- 8.8 h
- Estimated system availability
- 99.8875 %
- Expected downtime per year
- 9.9 h
- Meets the target
- No
Components in series (each line may be redundant)
| Component | Each | Copies | Combined |
|---|---|---|---|
| Internet link | 99.5 % | 2 | 99.9975 % |
| Firewall | 99.95 % | 2 | 99.99997 % |
| Load balancer | 99.99 % | 1 | 99.99 % |
| Web servers | 99.5 % | 3 | 99.99999 % |
| Database | 99.9 % | 1 | 99.9 % |
Downtime budget
| Period | Allowed downtime |
|---|---|
| Per day | 86.4 s |
| Per week | 10.1 min |
| Per month (30.44 days) | 43.8 min |
| Per quarter | 2.2 h |
| Per year | 8.8 h |
Common targets
| Availability | Per day | Per week | Per month (30.44 days) | Per quarter | Per year |
|---|---|---|---|---|---|
| 99 % | 14.4 min | 100.8 min | 7.3 h | 21.9 h | 3.7 days |
| 99.5 % | 7.2 min | 50.4 min | 3.7 h | 11 h | 43.8 h |
| 99.9 % | 86.4 s | 10.1 min | 43.8 min | 2.2 h | 8.8 h |
| 99.95 % | 43.2 s | 5 min | 21.9 min | 65.8 min | 4.4 h |
| 99.99 % | 8.6 s | 60.5 s | 4.4 min | 13.2 min | 52.6 min |
| 99.999 % | 864 ms | 6 s | 26.3 s | 78.9 s | 5.3 min |
- Components in series multiply their availabilities; n redundant copies give 1 − (1 − A)ⁿ, assuming independent failures and instant failover — real systems share power, software and people, so treat the result as an upper bound.
- Check how your contract measures availability: scheduled maintenance, measurement interval and partial outages are often excluded.
使用方法: 可用性与 SLA 计算器
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英语技术说明
Assumes independent failures and instant failover; real systems share risks, so the composite figure is an upper bound. Everything is calculated in your browser; nothing is sent or probed on the network.
Downtime = period × (1 − availability). Components in series multiply; n redundant copies give 1 − (1 − A)ⁿ; MTBF ÷ (MTBF + MTTR) gives a unit’s availability.
99.9 % allows 8.8 hours of downtime a year or 43.8 minutes a month; two 99.5 % links in parallel reach 99.9975 %.