3-sites: two active sites + tie-breaker in 3rd site (optional)
HPE SimpliVity calls the tie-breaker "arbiter". The use of the arbiter automates failover decisions in order to avoid split-brain scenarios like network partitions and remote site failures. The arbiter can be either on-premises or hosted as a cloud instance, and is recommended but not a hard requirement. The arbiter is a small Windows service, so it can run about anywhere, as long as it has network access to both active sites.
Currently for Microsoft Hyper-V environments (2-node clusters) the "arbiter is a hard requirement.
The HPE OmniStack 3.7.9 version of Arbiter introduces support for clusters with hosts that use HPE OmniStack 3.7.8 and other clusters with hosts that use HPE OmniStack 3.7.9. The federation can contain a mix of clusters with those two versions. However, all the hosts within the same cluster must use the same version.
HPE, SimpliVity [HCI]/3.7.10, 380
SC Configuration, Disaster Recovery, Data Availability