Replicas: 0-3 Replicas (1N-4N) at each active site
Erasure Coding: RAID5-6 at each active site
VMware vSAN 6.6 introduced enhanced stretched cluster availability with Local Fault Protection. You can provide local fault protection for virtual machine objects within a single site in a stretched cluster. You can define a Primary level of failures to tolerate for the cluster, and a Secondary level of failures to tolerate for objects within a single site. When one site is unavailable, vSAN maintains availability with local redundancy in the available site.
In the case of stretched clustering, selecting 0 replicas means that there is only one instance of the data available at each of the active sites.
Local Fault Protection is only available in the Enterprise edition of vSAN.
VMware, vSAN [SDS]/7.0 U1, Enterprise
SC Data Redundancy, Disaster Recovery, Data Availability