You are configuring a Virtual Machine Scale Set (VMSS) named `vmss-worker` that runs a CPU-bound processing service. The VMSS is configured with a minimum instance count of 2 and a maximum instance count of 10. The scale-out rule is configured to increase the instance count by 1 when the average CPU percentage is greater than 75% for 10 minutes. You need to configure a scale-in rule that decreases the instance count by 1 when the workload decreases. The scale-in rule must prevent thrashing (immediate scale-in) when the scale set is running at its minimum capacity of 2 instances and triggers a scale-out. Which of the following is the maximum CPU percentage threshold you should configure for the scale-in rule?
- 45%Cevap
- B55%
- C60%
- D70%
Cevap
45%
The threshold of 45% is the only option that is strictly below 50%. When the scale set scales out from 2 instances (exceeding 75% average CPU, or 150% total CPU load) to 3 instances, the workload is distributed, reducing the average CPU per instance to 50%. A scale-in threshold of 45% ensures the new workload level (50%) does not trigger an immediate scale-in event, avoiding thrashing.
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Anahtar Kavram
To prevent VMSS autoscale thrashing, the scale-in metric threshold must be set lower than the expected resource usage per instance after a scale-out event occurs.