The nature of Amazon EC2 instances and other AWS services

Question

I have some basic (stupid) questions about AWS EC2 instances or AMIs.

I created a directory and some test file to check if files persist beyond instance stop and start.

When I'm about to stop my Ubuntu instance I get this warning:

Are you sure you want to stop this instance? Warning: Please note that any data on the ephemeral storage of your instance will be lost when it is stopped.

But when I start the Ubuntu instance again my test dir and file is still there, persisting. What is this warning about?

If I can install MySQL, GlassFish server etc. on this instance, when does the need for Amazon Relational Database Service (RDS), DynamoDB and Storage Gateway come in? Are these last mentioned AWS services for larger scale enterprises that need more reliability and scalability, but not really for private users that do not require much storage?

Hm, my current understanding is that storage in EC2 instances are safe as long as (duh) I don't delete them, and data in RDS and Storage Gateway etc. will survive instance deletion. Assuming that as long as I have been given full control of the life of EC2 instances, I shouldn't be worried.

Cheers.

Answer 1

ephemeral storage is a special kind of storage that is not active by default (on my instances).