You can add hosts to your SDDC cluster or remove hosts from your SDDC cluster as long as the number of hosts does not fall below the minimum or above the maximum for your SDDC.

The minimum number of hosts in an SDDC cluster is 4. The maximum number hosts depends on various factors, including what kind of account you signed up for.

When you add a host to the SDDC, it is added to the existing cluster in the SDDC, and its storage becomes part of the vSAN storage for the cluster.