To support more tenant workloads or to improve the availability of workloads in a workload domain cluster, you can add hosts to the cluster.

Figure 1. Adding Hosts to a Cluster in a Workload Domain


  • The maximum number of VMware ESXi™ hosts in a cluster is 64. However, before scaling a cluster to this limit, consider the implications for life-cycle management of that cluster.

    • Where life-cycle operations require that you place hosts in maintenance mode, the more hosts in a cluster, the longer it takes to complete the upgrade of the cluster. Consider the time for these operations in relation to your maintenance windows.

    • Choose a cluster size that provides a balance between the number of clusters and the size of the cluster.

  • If the time period between the deployment of the original hosts and the purchase of new hosts is significant, the specifications of the deployed and new hosts might be different.

    • If you disabled Enhanced vMotion Compatibility (EVC) processor support for a cluster in VMware vSphere® after implementing VMware Validated Design, and you must enable it again to add new hosts, then all virtual machines must be powered off to perform the change.

    • The impact of the EVC configuration is even more significant in the context of the Consolidated SDDC architecture where the management virtual machines must be powered off in addition to the workloads.

    • If EVC must remain disabled, then adding hosts of a different specification to the cluster is not an option. Consider adding a cluster to an existing workload domain or deploying a workload domain and adding the cluster there.

  • Increasing the number of hosts in a cluster means that vSphere DRS can automatically redistribute existing and new workloads efficiently across all hosts.

  • When adding hosts to a VMware vSAN™ cluster, the vSAN requirements for the number of failures to tolerate (FTT) have been already satisfied. As a result, the available capacity increases by the full amount of storage added.

  • When adding hosts to a cluster consider keeping all cluster nodes connected to the same pair of Top-of-Rack (ToR) switches for locality of the traffic for vSphere vMotion and vSAN, and for simplified network configuration outside the cluster.

    If the configuration of the existing physical rack infrastructure does not support connecting new hosts to the same ToRs that are used by the existing cluster nodes, then you might be creating a situation where non-deterministic network performance exists for certain intra-cluster operations.

  • The maximum number of workloads that is supported per cluster is 8,000.