Merge pull request #3860 from edx/jibsheet/ssd‽

Switch to gp2 disks

playbooks/roles/launch_ec2/tasks/main.yml

@@ -50,6 +50,7 @@
       - device_name: /dev/sda1
         volume_size: "{{ root_ebs_size }}"
         delete_on_termination: true
+        volume_type: "gp2"
     zone: "{{ zone }}"
     instance_profile_name: "{{ instance_profile_name }}"
     user_data: "{{ user_data }}"