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High Availability
High Availability can also be called Uptime. Refers to the accessibility of a system that can operate without any interruptions for an extended period.
What’s the difference between the following?
- 99%
- 99.9%
- 99.99%
- 99.999%
Availability Levels and Downtime
99% Availability (Two Nines):
- Downtime: ~3.65 days per year
- Monthly Downtime: ~7.2 hours
- This level is common for non-critical systems where some downtime is tolerable.
99.9% Availability (Three Nines):
- Downtime: ~8.76 hours per year
- Monthly Downtime: ~43.8 minutes
- Suitable for many business applications with occasional tolerance for downtime.
99.99% Availability (Four Nines):
- Downtime: ~52.6 minutes per year
- Monthly Downtime: ~4.38 minutes
- Often used for critical applications where downtime can have significant business impacts.
99.999% Availability (Five Nines):
- Downtime: ~5.26 minutes per year
- Monthly Downtime: ~26.3 seconds
- Known as “five nines,” this level is aimed at highly critical systems, such as those in healthcare, finance, or telecommunications, where even a few minutes of downtime is unacceptable.
As per the Gartner survey, it costs $5,600 per minute.
https://blogs.gartner.com/andrew-lerner/2014/07/16/the-cost-of-downtime/