A virtual datastore is either an ordinary datastore or a stretched datastore. The former is for standard HCI clusters, while the latter is for stretched HCI clusters.

You don't need to specify the number of replicas when initializing a virtual datastore, as it is determined based on the number of VMs. There are two-replica or three-replica modes.

To use a three-replica cluster with three or four hosts, you need to have at least three hosts per ordinary datastore and two disk groups per host. If your cluster has five or more hosts, there are no limits on the disk group.

A disk group can contain SSDs and HDDs or only SSDs. In the above figure, the host has two disk groups.