1. What is AWS Availability?

AWS availability refers to the percentage of time a service is operational and accessible to users. It's a key metric for measuring the reliability of cloud services and is typically expressed as a percentage or decimal value.

2. How Does the Calculator Work?

The calculator uses the availability equation:

Where:

• \( Total\ Time \) — The total observation period (hours)
• \( Downtime \) — The time the service was unavailable (hours)

Explanation: The equation calculates the proportion of time the service was available during the observation period.

3. Importance of Availability Calculation

Details: Availability is crucial for service level agreements (SLAs), system reliability assessments, and infrastructure planning. AWS typically offers availability between 99.9% to 99.99% for most services.

4. Using the Calculator

Tips: Enter total time in hours and downtime in hours. Both values must be positive numbers, and downtime cannot exceed total time.

5. Frequently Asked Questions (FAQ)

Q1: What's considered good availability for AWS services?
A: AWS typically guarantees 99.9% (three nines) to 99.99% (four nines) availability depending on the service and SLA.

Q2: How does this relate to AWS SLA credits?
A: If availability falls below the guaranteed level, AWS may provide service credits according to their SLA terms.

Q3: Should planned maintenance be counted as downtime?
A: Typically, AWS SLAs exclude planned maintenance from downtime calculations, but you may include it for internal metrics.

Q4: How can I improve my AWS availability?
A: Use multi-AZ deployments, implement auto-scaling, design for failure, and follow AWS best practices for high availability.

Q5: What's the difference between availability and uptime?
A: Uptime is the total time a system is operational, while availability is the percentage of time the system is operational during a given period.