Examples in known open source worlds...
If you run ProxMox with DRBD on the Debian (host) layer, it's RLS assuming ProxMox has local disks.
If you then make that block storage available over the network, it becomes a SAN (a traditional / physical SAN.) A SAN with replication for resiliency.
If you run ProxMox and make a VM of Ubuntu and in that VM install DRBD it may or may not be RLS depending on where the host is getting its storage from for that VM. To the VM it will appear as if it is RLS, but we really don't know unless we check the stack. It's just the replication piece here.
If you then make that DRBD block layer in the VM available over the network, it becomes a vSAN.