Amazon Elastic Container Service
Developer Guide (API Version 2014-11-13)

Storage Configuration

By default, the Amazon ECS-optimized Amazon Linux 2 AMI ships with a single 30-GiB root volume. You can modify the 30-GiB root volume size at launch time to increase the available storage on your container instance. This storage is used for the operating system and for Docker images and metadata.

The default filesystem for the Amazon ECS-optimized Amazon Linux 2 AMI is ext4, and Docker uses the overlay2 storage driver. For more information, see Use the OverlayFS storage driver in the Docker documentation.