Although VSAN supports 100 VMs per ESXi host in the VSAN cluster, vSphere HA can only protect a total of 2,048 virtual machines per datastore.
In a VSAN environment, vSphere HA agents communicate over the VSAN network. The reasoning behind this is that in the event of a network failure the vSphere HA and VSAN hosts to be part of the same partition.
If the VSAN and management networks are on a different physical infrastructure, it is recommended to change the default vSphere HA isolation address from the management network to the VSAN network. By default, the isolation address is the default gateway of the management network.
VMware’s recommendation when using vSphere HA with VSAN is to use an IP address on the VSAN network for isolation.
If changes are made at the VSAN layer to the VSAN networks, this is not automatically detected by vSphere HA. Therefore, a vSphere HA cluster reconfiguration must be manually initiated by the vSphere administrator for these changes to be detected.
A Virtual SAN datastore cannot be used for datastore heartbeating. However, if you have storage that can be reached by an alternate network path that is independent of the Virtual SAN network, you can use it to set up a heartbeat datastore.