EC2 OS disk pricing

The answer is it depends. You have two types of instances:

• instances with EBS-backed storage
• instances with ephemeral (local) storage There are fundamental differences between the 2, one of the main ones is cost as the first one is charged per GB and the second one is free.

When you create an estimate using the calculator, you have a section for EBS volumes when you configure an EC2 instance in your estimate. Any EBS that will be used can be added there, or as a separate entry. Obviously, you don't need to add any ephemeral storage as it is free. However, any data stored on your ephemeral storage will be lost when the instance is stopped or restarted so you need to be careful which usage you make of it.

When you add an instance to your estimate, you have the following information for the optional section where you can add EBS: "Amazon Elastic Block Store (EBS) allows you to create storage volumes and attach them to Amazon EC2 instances. Once attached, you can create a file system on top of these volumes, run a database, or use them in any other way you would use block storage."

730h is the average number of hours in a month over a non-leap year (i.e. 365 * 24 / 12)

You can create LVM on top of your EBS for your root and data storage device, that's not an issue.

You are right on point 3 if I understand what you mean. If you want to estimate your actual EC2 cost for 360 hours, and you want to retain your EBS volumes when your instance is stopped, you need to add your EBS storage separately in the estimate, otherwise instance utilization is also going to impact EBS cost.