The use of the Stretched Cluster Witness Appliance automates failover decisions in order to avoid split-brain scenarios like network partitions and remote site failures. The witness is deployed as a VM within a third site.

vSAN 6.7 introduced the option to configure a dedicated VMkernel NIC for witness traffic. This enhances data security because witness traffic is isolated from vSAN data traffic.

vSAN 7.0 U1 introduces the vSAN Shared Witness. This feature allows end-user organizations to leverage a single Witness Appliance for up to 64 stretched clusters. This is especially useful in scenarios where many edge locations are involved. The size of the Witness Appliance determines the maximum number of cluster and components that can be managed.