As the SDDC expands, you can configure additional compute-only clusters. Tenant workloads run on the ESXi hosts in the compute cluster instances. Multiple compute clusters are managed by the Compute vCenter Server instance. The design determines vSphere HA settings for the compute cluster.

Table 1. Design Decisions on the Compute Cluster

Decision ID

Design Decision

Design Justification

Design Implication

SDDC-VI-VC-035

For a single availability zone, configure vSphere HA to use percentage-based failover capacity to ensure n+1 availability.

Using explicit host failover limits the total available resources in a cluster.

The resources of one ESXi host in the cluster is reserved which can cause provisioning failure if resources are exhausted.

SDDC-VI-VC-036

When using two availability zones, configure Admission Control for percentage-based failover based on half of the ESXi hosts in the cluster.

For example, in a cluster with 8 ESXi hosts you configure admission control for 4 ESXi hosts failure and percentage-based failover capacity.

Only half of a stretched cluster should be used to ensure that all VMs have enough resource in the event of an availability zone outage.

If you add more ESXi hosts to the compute cluster, you must add them in pairs, one in each availability zone.