An administrator is configuring an Azure Virtual Machine Scale Set (VMSS) named VMSS1 that uses Uniform orchestration. VMSS1 currently has five instances running a web application, and the upgrade policy is set to Manual. You need to configure VMSS1 to meet the following requirements:
- When a new version of the OS image is published, the instances must be updated automatically in batches to prevent application downtime.
- VMSS1 must scale out by two instances when the average CPU utilization exceeds for 10 minutes.
- VMSS1 must scale in by one instance when CPU utilization drops, but you must prevent rapid scaling loops (thrashing).
Which two configuration settings should you implement? (Select two.)
- Change the upgrade policy of VMSS1 to Rolling.Answer
- BChange the upgrade policy of VMSS1 to Automatic.
- Configure a scale-in rule with an average CPU threshold of and a cooldown period of 10 minutes.Answer
- DConfigure a scale-in rule with an average CPU threshold of and a cooldown period of 1 minute.
Answer
To configure the scale set correctly, you must change the upgrade policy to Rolling to ensure updates occur in batches without causing application downtime, and configure a scale-in rule with a low CPU threshold (such as ) and an adequate cooldown period (such as 10 minutes) to prevent instance thrashing.
The Rolling upgrade policy updates instances in batches, which prevents downtime by keeping a subset of instances online. To prevent instance thrashing, the scale-in metric threshold must be set significantly lower than the scale-out threshold, and the cooldown period must be long enough to let the system stabilize after scaling actions.
Step-by-Step Solution
Key Concept
Configuring Virtual Machine Scale Set upgrade policies and preventing autoscale thrashing.