If you are taking the AWS Solutions Architect Associate certification test – you need to know this:
While EBS volumes are durable (data is not removed / released) when an instance is stopped, only when an instance is terminated are EBS volumes removed / storage released.
Instance stores are released when an instance is stopped and or terminated. When an EC2 instance is rebooted – technically the instance is NOT stopped so ephemeral storage like instance stores remain intact / durable during a reboot.
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