To support more tenant workloads and improve high availability and isolation, you can plan to add more clusters to a workload domain.

You are considering increasing the number of clusters in a workload domain for one of the following reasons:

  • Support increasing the number of workloads in the workload domain.

  • Improve the availability of workloads in the workload domain.

  • Improve the separation of workloads in the workload domains for security, licensing, or other reasons.
Figure 1. Adding a Cluster to a Workload Domain


Considerations

  • By adding clusters you can distribute workloads across additional fault domains.

  • When using multiple clusters, you can perform parallel host upgrades across several clusters as part of life-cycle operations on the hosts.

  • Having more rather than less clusters in a workload domain causes loss of efficiency in some areas:

    • Global reduction in the efficiency of vSphere DRS because workloads can balance only within each cluster, and not across all hosts in the workload domain.

    • vSAN efficiency is lower because you allocate capacity for vSAN redundancy in each new cluster to accommodate a target vSAN FTT.

  • Consider the granularity at which you might like to perform upgrades of vCenter Server, vSphere cluster, and ESXi hosts. If all components in a workload domain must be upgraded together, the size of the maintenance window required to complete the upgrade of vCenter Server and all clusters it manages is important. Deploying an additional workload domain might be required simply to make the upgrade of a workload domain in a single window possible.

  • For efficient network traffic flow between clusters, you should extend the transport zones in VMware NSX® Data Center for vSphere® to include the new clusters.

  • Consider the location of the NSX Edge devices that route traffic into and out of the environment and whether the infrastructure for these edges can handle the extra network traffic without a negative impact on the existing workloads.