ec2-create-image command line tool has a
--block-device-mapping option to define the volumes associated with new instances.
In your specific case, you may want to suppress the automatic creation and attaching of the database volume by specifying something like:
ec2-create-image --block-device-mapping /dev/sdh=none [...]
This will let you create and attach your own volumes to the new instances.
Alternatively, you could specify that an empty volume be created an attached when a new instance is started:
ec2-create-image --block-device-mapping /dev/sdh=:20:false [...]
When you run an instance, you could override the size of that volume using the
--block-device-mapping option to
It's also worth learning about the
delete-on-termination flag for
--block-device-mapping so that you understand how to control whether your second volume should automatically be deleted when the instance is terminated.