High I/O instances are storage optimized. Examples of this family are H1 (high disk throughput), I3 (high random I/O performance), and D2 (dense storage). EBS-optimized instances have exclusive capacity for I/O operations.
RDS is not compatible with Oracle Enterprise High Availability options because it uses Multi-AZ and access to the OS is limited. Also, note that burstable performance instances are not compatible with EBS optimizations.