vSphere: 3-sites = two active sites + tie-breaker in 3rd site
The use of a Witness Server automates failover decisions in order to avoid split-brain scenarios like network partitions and remote site failures. The witness is deployed as a small VM on a third site.
The RTT to the third site should not exceed 200ms and there should be at least 100Mbps of bandwidth available.
Cisco, HyperFlex [HCI]/4.0, x86
SC Configuration, Disaster Recovery, Data Availability