For vSAN you require licensing for ESXi and also vSAN - which of each of these depends on requirements:
e.g. if DRS is a requirement then you need Enterprise edition ESXi/vSphere licensing.
Are the data-nodes going to be in different physical locations and if so, approximately how many milliseconds over the network from site to site (and sites to Witness)?
Typically stretched-clusters require Enterprise vSAN licensing, however 2-node stretched-clusters only require vSAN Standard or ROBO licensing:
Hope this helps.
Thanks for the reference articles.
At present each site is 3 km in distance apart, <1 ms between all three sites as there is fiber (10Gb between data and 1 Gb to witness) joining each. There are only two servers + witness appliance for this setup.
That will work fine for stretched-cluster - was just checking to make sure as Round Trip Time (RTT) of 5msec is the max supported for stretcehd between data-sites, the lower the better of course.
Latest reference guides for stretched-clusters: