You can use Virtual SAN as the shared storage for a vSphere HA cluster. If enabled, Virtual SAN aggregates the specified local storage disks available on the hosts into a single datastore shared by all hosts.

To use vSphere HA with Virtual SAN, you must be aware of certain considerations and limitations for the interoperability of these two features.

For information about Virtual SAN, see Administering VMware Virtual SAN.

Note:

You can use vSphere HA with Virtual SAN stretched clusters.

ESXi Host Requirements

You can use Virtual SAN with a vSphere HA cluster only if the following conditions are met:

  • All the cluster's ESXi hosts must be version 5.5 or later.

  • The cluster must have a minimum of three ESXi hosts.

Networking Differences

Virtual SAN has its own network. If 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. vSphere HA uses the management network only if Virtual SAN is disabled. vCenter Server chooses the appropriate network if vSphere HA is configured on a host.

Note:

You can enable Virtual SAN only if 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. 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.

The following table shows the differences in vSphere HA networking whether or not Virtual SAN is used.

Table 1. 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, you must coordinate this setting 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 that the vSphere HA admission control setting reserved.

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 vSphere HA reserves less capacity, failover activity might be unpredictable. Reserving too much capacity overly constrains the powering on of virtual machines and intercluster vSphere vMotion migrations.