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:
| Timeframe | Possible Downtime |
|---|---|
| Daily | 1 minute, 26 seconds |
| Weekly | 10 minutes, 4 seconds |
| Monthly | 43 minutes, 49 seconds |
| Quarterly | 2 hours, 11 minutes, 29 seconds |
| Yearly | 8 hours, 45 minutes, 57 seconds |
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. Customer Assurance: SLAs provide customers with confidence that the service will be reliable and meet their business needs.
- 2. Accountability: By setting clear expectations and metrics, SLAs hold service providers accountable for maintaining service levels.
- 3. Performance Benchmarking: SLAs serve as a benchmark for evaluating the performance and reliability of the service over time.
- 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 Percentage | Daily Downtime | Monthly Downtime | Yearly Downtime |
|---|---|---|---|
| 99.0% | 14.4 minutes | 7.2 hours | 3.65 days |
| 99.9% | 1.44 minutes | 43.2 minutes | 8.76 hours |
| 99.99% | 8.64 seconds | 4.32 minutes | 52.56 minutes |
| 99.999% | 0.864 seconds | 25.9 seconds | 5.26 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. 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. 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. Calculate the Uptime: Use the following formula to calculate the uptime percentage: ((Total Time - Total Downtime) / Total Time) x 100