Your EC2 instance with instance-store storage when stopped can be launched on any other random host in the AZ when you power it back on. Since your rootdisk is an EBS volume attached across the network, so when you start your instance back up you're going to be launched likely somewhere else with an empty slot, and empty local-storage. This is why there is always a disclaimer that this local storage is ephemeral and don't count on it being around long-term.

I think the parent was agreeing with you. If the “local” SSDs _weren’t_ actually local, then presumably they wouldn’t need to be ephemeral since they could be connected over the network to whichever host your instance was launched on.

It is because on reboot you may not get the same physical server . They are not rebooting the physical server for you , just the VM

Same VM is not allocated for a variety of reasons , scheduled maintenance, proximity to other hosts on the vpc , balancing quiet and noisy neighbors so on.

It is not that the disk will always wiped , sometimes the data is still there on reboot just that there is no guarantee allowing them to freely move between hosts

Data persists between reboots, but not shutdowns:

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-inst...

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-inst...