Merge pull request #4059 from edx/feanil/fix_mounts

Determine the size of the root volume not sdf

playbooks/continuous_delivery/launch_instance.yml

@@ -76,7 +76,7 @@
       vpc_subnet_id: "{{ ec2_vpc_subnet_id }}"
       assign_public_ip: "{{ ec2_assign_public_ip }}"
       volumes:
-        - device_name: /dev/sdf
+        - device_name: /dev/sda1
           volume_type: 'gp2'
           volume_size: "{{ ebs_volume_size }}"
       wait: yes