7.3.1 vSAN Witness
As highlighted in the previous section, the vSAN witness is used in place of having a third site of hosts for the redundancy provided by vSAN. With both stretched cluster and two-node cluster configurations, the witness stores components of virtual machines and is used to monitor both of the sites.
The witness can be either an ESXi host that resides in another site and has reliable network connectivity to the vSAN cluster, or the vSAN witness appliance can be used. Either way, it is added to the cluster during the configuration of stretched clustering.