You can encrypt data-in transit in your vSAN cluster, and encrypt data-at-rest in your vSAN datastore.
vSAN can encrypt data in transit across hosts in the vSAN cluster. Data-in-transit encryption protects data as it moves around the vSAN cluster.
vSAN can encrypt data at rest in the vSAN datastore. Data-at-rest encryption protects data on storage devices, in case a device is removed from the cluster.