I saw multiple posts here on Isolation and role Heartbeat datastore "could" plays. I also read Deep Dive 6.7. Based on my understanding, would be the right way to defend the decision?
Decision:
vSAN heartbeat datastore will be disabled in the vSAN Stretch cluster?
Justification:
vSAN has a single datastore. When ESXi host is isolated it will try to confirm by trying to reach vSAN network default gateway in the respective site. If vSAN GW ist not reachable, it is as sufficient validation to confirm ESXi host is isolated. In other words, ESXi host has lost connectivity to other components and effectively lost connectivity to datastore. Enabling heartbeat datastore will be of little effect as in our case all Networks (vSAN, MGMT, etc) flows through the same network cards a situation similarly in a converged network. The possibility of vSAN network unavailable and ESXi host reachable on other networks is almost zero.
Design Implication:
There could be a corner case when ESXi host is unable to declare itself isolated but at the same time will lose locks on the vSAN datastore, vSphere HA will trigger vSphere HA response and potential two VM with same MAC, IP might be running in the environment.
Additional Settings:
1. Isolation Response set to power off
2. vSAN subnet's Isolation address configured in the Availability zones
3. Disabled default Isolation address