Your configuration must have a minimum of two Oracle servers to fill the role of control and compute nodes.
All compute nodes should be identical in hardware configuration, memory, and software installed.
All compute nodes must have significant RAM.
A general guideline is to assume 4 GB or more for each instance VM, and reserve at least 4 GB of RAM for overhead and additional processing power. For example, if the compute node has only 16GB of RAM it could run three, 4-GB instance VMs.