Question 1

What is 99.9% uptime in minutes per month?

Accepted Answer

99.9% uptime allows 43.83 minutes (approximately 43 minutes and 50 seconds) of downtime per month, or about 8 hours and 45 minutes per year.

Question 2

What is the difference between 99.9% and 99.99% uptime?

Accepted Answer

99.9% allows about 43.8 minutes of monthly downtime while 99.99% allows only about 4.38 minutes. The difference is a factor of 10 in allowed downtime.

Question 3

What does five nines (99.999%) uptime mean?

Accepted Answer

99.999% uptime means no more than 5.26 minutes of downtime per year, or about 26 seconds per month. This is the gold standard for mission-critical systems.