Agreed SLA Uptime:

%

What does an SLA Agreement of 99.9% mean?

An SLA level of 99.9% uptime/availability allows for the following periods of downtime/unavailability:

2 hours, 11 minutes, 29 seconds8 hours, 45 minutes, 57 seconds
TimeframePossible Downtime
Daily1 minute, 26 seconds
Weekly10 minutes, 4 seconds
Monthly43 minutes, 49 seconds
Quarterly
Yearly

The SLA calculations are based on the assumption of a continuous uptime requirement, meaning the system must be operational 24/7 throughout the entire year. This includes all days, weekends, and holidays without any planned downtime. Additional approximations and considerations are applied as detailed in the source, ensuring a comprehensive and accurate reflection of the expected service availability.

What is an SLA?

A Service Level Agreement (SLA) is a formal contract between a service provider and a customer that outlines the expected level of service, including performance metrics and guarantees. In the context of uptime and downtime, an SLA specifically addresses the availability and reliability of a service, such as a website, application, or IT infrastructure.

Why is the Uptime/Downtime important?

  1. 1. Customer Assurance: SLAs provide customers with confidence that the service will be reliable and meet their business needs.
  2. 2. Accountability: By setting clear expectations and metrics, SLAs hold service providers accountable for maintaining service levels.
  3. 3. Performance Benchmarking: SLAs serve as a benchmark for evaluating the performance and reliability of the service over time.
  4. 4. Dispute Resolution: In case of service level disputes, the SLA serves as a reference document for resolving issues and determining appropriate remedies.

What is a good uptime percentage?

A good uptime percentage for most services and applications is typically 99.9% or higher. Here's a breakdown of what different uptime percentages mean in terms of allowable downtime over various time periods:

Uptime PercentageDaily DowntimeMonthly DowntimeYearly Downtime
99.0%14.4 minutes7.2 hours3.65 days
99.9%1.44 minutes43.2 minutes8.76 hours
99.99%8.64 seconds4.32 minutes52.56 minutes
99.999%0.864 seconds25.9 seconds5.26 minutes

Understanding Good Uptime:

  • 99.9% Uptime (Three Nines):This is a common standard for many businesses, translating to about 43.2 minutes of downtime per month. It strikes a balance between high availability and practical maintenance requirements.
  • 99.99% Uptime (Four Nines):This is a higher standard often used by critical applications where even minor downtime can significantly impact operations. It allows for only about 4.32 minutes of downtime per month.
  • 99.999% Uptime (Five Nines):Known as "high availability," this level is used by services where downtime must be minimized to almost zero, such as in financial services, healthcare systems, and other mission-critical applications. It allows for just about 25.9 seconds of downtime per month.

How to calculate Uptime?

Calculating uptime is essential for understanding the availability and reliability of a service. Uptime is typically expressed as a percentage and represents the amount of time a system is operational over a specific period. Here’s a step-by-step guide on how to calculate uptime:

  1. 1. Define the Total Time Period: Determine the total time period over which you want to calculate uptime. This could be daily, monthly, or yearly.
  2. 2. Measure the Downtime: Record the total amount of downtime within the defined period. Downtime is the period when the service is not operational and can be measured in hours, minutes, or seconds.
  3. 3. Calculate the Uptime: Use the following formula to calculate the uptime percentage: ((Total Time - Total Downtime) / Total Time) x 100