Five nines or 99.999% availability

Luca Spiller
Head of Engineering
January 10, 2024

What is five nines?

Availability or uptime is commonly quantified as a percentage, indicating the amount of time that a service is operational within a specific period. When we talk about five nines availability, we're referring to an impressive 99.999% uptime. This is the gold standard for many cloud providers. This translates to a downtime of less than 5 minutes and 13 seconds per year. Achieving 100% uptime would signify uninterrupted service, available 24/7 without any breaks.

What is an SLA?

Service providers typically set service-level agreements (SLAs) to define the expected service standards. These agreements often include a clause outlining the required availability, often expressed in a specific number of nines. Should the provider's downtime exceed this specified threshold, the SLA commonly mandates compensation for the customer, often in the form of a credit applicable to future services.

100% Availability Goal

The goal of any high-availabily system is 100% availabilty, however in reality problems happen and that is not always achiveable. If a provider offers a SLA, it reflects their confidence in their platform and the level of uptime it will achieve. High availability and uptime is important, as even a short amount of downtime can lead to substantial financial losses - imagine the impact from the stock market being down for 5 minutes.

How to prevent downtime?

A key part of preventing downtime is to have monitoring systems in place. WatchSumo can monitor your website, and alert you of issues before your website goes down. For example, an increase in the response time indicates something is wrong and could result in downtime - WatchSumo watches your website for this, and will alert you before your website goes down.

Calculating Downtime

99.999% in a day = 0.86s of downtime

99.999% in a week = 6s of downtime

99.999% in a month = 26s of downtime

99.999% in a quarter = 1 minute and 18 seconds of downtime

99.999% in a year = 5 minutes and 13 seconds of downtime

Other percentiles

Five nines of uptime is just one amount, other common 'nines' are as follows: