## What are nines of availability?

People typically talk in terms of nines of availability, which expresses system availability (uptime) as a percentage of total system time. Availability at 99% is OK as far as it goes, but that equates to more than seven hours of downtime per month.

## What does a 99.99 percent availability mean?

Five-nines availability — or 99.999% — is the percentage of time a network component or service is accessible to a user in a given period, usually defined as a year. The migration from private networks to cloud services has led companies to demand that service providers offer five-nines availability.

**How many 9’s of availability are required?**

The accepted availability standard for emergency response systems is 99.999% or “five nines” – or about five minutes and 15 seconds of downtime per year (see table below). To achieve five nines, all components of the system must work seamlessly together.

**What is the meaning of high availability?**

High availability (HA) is the ability of a system to operate continuously without failing for a designated period of time. HA works to ensure a system meets an agreed-upon operational performance level.

### How many minutes per month of downtime is 99.99 availability?

An uptime of 99.99% translates to about five minutes of total downtime per month.

### What does 99.9% uptime mean?

Uptime is the amount of time that a service is available and operational. Uptime is generally the most important metric for a website, online service or web based provider and is expressed as a percentage such as ‘99.9%’. For example a 99.9% uptime equates to 43 minutes and 50 seconds of downtime.

**How many 9s SLA are there?**

three 9’s

Percentage availability

Description | Up-time | Downtime per month |
---|---|---|

three 9’s | 99.9% | ~43 minutes |

three and a half 9’s | 99.95% | ~21 minutes |

four 9’s | 99.99% | ~4.3 minutes |

five 9’s | 99.999% | ~25 seconds |

**What does 4 nines mean?**

The industry generally recognizes this as very reliable uptime. A step above, 99.99%, or “four nines,” as is considered excellent uptime. But four nines uptime is still 52 minutes of downtime per year. Consider how many people rely on web tools to run their lives and businesses. A lot can go wrong in 52 minutes.

#### What is 99.9% uptime in a year?

Percentage calculation

Availability % | Downtime per year | Downtime per month |
---|---|---|

99.5% (“two and a half nines”) | 1.83 days | 3.65 hours |

99.8% (“two and seven eighths nines”) | 17.53 hours | 87.66 minutes |

99.9% (“three nines”) | 8.77 hours | 43.83 minutes |

99.95% (“three and a half nines”) | 4.38 hours | 21.92 minutes |

#### How many hours is 99.9 downtime?

Percentage calculation

Availability % | Downtime per year | Downtime per day (24 hours) |
---|---|---|

99.5% (“two and a half nines”) | 1.83 days | 7.20 minutes |

99.8% (“two and seven eighths nines”) | 17.53 hours | 2.88 minutes |

99.9% (“three nines”) | 8.77 hours | 1.44 minutes |

99.95% (“three and a half nines”) | 4.38 hours | 43.20 seconds |

**How is availability calculated?**

Availability = Uptime ÷ (Uptime + downtime) That equals 10 hours of total downtime.

**What is the downtime per day for a system showing 99.9% availability?**

SLA level of 99.9 % uptime/availability results in the following periods of allowed downtime/unavailability: Daily: 1m 26s.