6.0.1

n
The cluster must have a minimum of three ESXi hosts.
Networking Differences
Virtual SAN has its own network. When Virtual SAN and vSphere HA are enabled for the same cluster, the
HA interagent traffic flows over this storage network rather than the management network. The
management network is used by vSphere HA only when Virtual SAN is disabled. vCenter Server chooses
the appropriate network when vSphere HA is configured on a host.
NOTE Virtual SAN can only be enabled when vSphere HA is disabled.
If you change the Virtual SAN network configuration, the vSphere HA agents do not automatically pick up
the new network settings. So to make changes to the Virtual SAN network, you must take the following
steps in the vSphere Web Client:
1 Disable Host Monitoring for the vSphere HA cluster.
2 Make the Virtual SAN network changes.
3 Right-click all hosts in the cluster and select Reconfigure for vSphere HA.
4 Re-enable Host Monitoring for the vSphere HA cluster.
Table 2-2 shows the differences in vSphere HA networking when Virtual SAN is used or not.
Table 2‑2. vSphere HA networking differences
Virtual SAN Enabled Virtual SAN Disabled
Network used by vSphere HA Virtual SAN storage network Management network
Heartbeat datastores Any datastore mounted to > 1 host,
but not Virtual SAN datastores
Any datastore mounted to > 1 host
Host declared isolated Isolation addresses not pingable and
Virtual SAN storage network
inaccessible
Isolation addresses not pingable and
management network inaccessible
Capacity Reservation Settings
When you reserve capacity for your vSphere HA cluster with an admission control policy, this setting must
be coordinated with the corresponding Virtual SAN setting that ensures data accessibility on failures.
Specifically, the Number of Failures Tolerated setting in the Virtual SAN rule set must not be lower than the
capacity reserved by the vSphere HA admission control setting.
For example, if the Virtual SAN rule set allows for only two failures, the vSphere HA admission control
policy must reserve capacity that is equivalent to only one or two host failures. If you are using the
Percentage of Cluster Resources Reserved policy for a cluster that has eight hosts, you must not reserve
more than 25% of the cluster resources. In the same cluster, with the Host Failures Cluster Tolerates policy,
the setting must not be higher than two hosts. If less capacity is reserved by vSphere HA, failover activity
might be unpredictable, while reserving too much capacity overly constrains the powering on of virtual
machines and inter-cluster vMotion migrations.
vSphere Availability
30 VMware, Inc.