Once we have selected our instance AMI and type, we also need to consider the storage options for our instance. Some instance types come with a so-called instance store, while others are only compatible with volumes that are created with the Elastic Block Storage (EBS) service.
Instance store and EBS volumes
The root device
When we create and launch a new instance, the operating system is run off the so-called root device. When we select a certain instance type, it will specify whether it has some instance store or whether it is backed by EBS. This will determine where the root device will be deployed and what the characteristics, as far as the data persistence and performance of the root device, will be.