For proof-of-concept deployments, you can deploy a 1-host cluster with just a Master host.
The Master host can run user workloads just as a worker host can when required for
demonstration purposes. For production deployments, you must have a reserved, dedicated
master host and separate worker host(s).
Even on multi-host
deployments, the Master host doubles up to perform both functions: those of the Master,
and those of a worker. Starting with version 1.4.3, multi-host deployments can be
customized to reserve the Master only for internal processes while user workloads are
run exclusively on workers. For details, see Reserving the Master Host for Internal CDSW