Using stateful instance actions, you can change the instance state while keeping its data and IPs.
In order to change the state, click on 'instances' tab and select the instance:
Pause - Equivalent to stopping the instance from AWS. All the data will be saved (According to the stateful configuration), the actual Spot instance will be terminated and when it will be resumed, it will be exactly in the same state in terms of data and network interfaces.
Resume - This will be used to start the instance after pausing it.
Recycle - Equivalent to rebooting or restarting the machine. Of course, all the data will be saved.
Deallocate - Release all resources (Root volume, data volumes, snapshot and network interfaces) and terminate the instance. When deallocating a machine, its data will be lost.
Please note: When downsizing your Elastigroup's capacity some resources will not be deleted although the instance will be terminated. to properly downsize the capacity, deallocate the relevant instances using the instances tab.