Ever Wondered How To Calculate GCP SLA Credit?

Let’s take a hypothetical situation. How would I calculate an estimated SLA if my application used services deployed on 1,000 Google Compute Engine instances? Assuming that the services were dependent on each other, would the estimated downtime per year of my application be 1,000 * 0.0001 = 0.10 or 10% per year?

SLA is not for only one VM instance, as per official documentation

"For virtual machine instances: Loss of external connectivity or persistent disk access for all running instances, when Instances are placed across two or more Zones in the same Region."

So the SLA will be tied to a specific zone. If that zone goes down for .01% of the month, that would be like 4:38 minutes.

For more information on scenarios and tools that could be useful check out these links: 

• Calculating composite SLA 

• SLA & Uptime calculator: How much downtime corresponds to 99.9 % uptime 

• Estimate Outage Credit