A company launches an EC2 instance from an instance-store-backed AMI for a workload that needs the full local NVMe scratch capacity. An engineer later tries to reduce cost by stopping the instance overnight, the same way they do for other instances in the fleet. What happens?
- The instance stops normally and can be started again later, exactly like an EBS-backed instance
- The stop action is not available; the instance can only be rebooted or terminated, never stopped
- The instance stops, but AWS automatically converts its root volume to an EBS volume first
- The instance hibernates instead of stopping, preserving the instance store contents
Why B? And why not the others?
Correct answer: B. The stop action is not available; the instance can only be rebooted or terminated, never stopped
Instance-store-backed instances use local host disk as their root volume, and because that root volume cannot be detached from the underlying hardware and reattached elsewhere, the EC2 console and API only offer reboot or terminate for these instances; stop and start are simply not available. The option describing a normal stop is wrong because that behavior applies only to EBS-backed instances, whose root volume persists on EBS storage independent of the host and can be reattached after the instance migrates to new hardware. Automatic conversion to an EBS volume does not happen on its own; producing an EBS-backed equivalent would require manually creating a new AMI and launching from it. Hibernation is also unavailable here because hibernating requires an encrypted EBS root volume to save the instance's RAM contents to, and an instance-store-backed instance has no such volume to write to.
Source: AWS EC2 documentation: Stop and start Amazon EC2 instances — instance store root volume restrictions