You can stretch a cluster in the management domain or in a VI workload domain across two availability zones within a region. Both availability zones must contain an equal number of hosts to ensure failover in case any of the availability zones goes down.

The default management vSphere cluster must be stretched before a VI workload domain cluster can be stretched. This ensures that the NSX-T Data Center control plane and management VMs (vCenter, NSX-T Data Center management cluster, and SDDC Manager) remain accessible if the stretched cluster in the primary availability zone goes down.
Note: You cannot stretch a cluster in the following conditions:
  • The cluster uses static IP addresses for the NSX-T Data Center Host Overlay Network TEPs.
  • The cluster has a vSAN remote datastore mounted on it.
  • The cluster uses vSphere Lifecycle Manager images.
  • The cluster shares a vSAN Storage Policy with any other clusters.
  • The cluster is enabled for Workload Management (vSphere with Tanzu).
Some use cases for stretching a cluster are described below.
  • Planned maintenance

    You can perform a planned maintenance on an availability zone without any downtime and then migrate the applications after the maintenance is completed.

  • Automated recovery

    Stretching a cluster automatically initiates VM restart and recovery, and has a low recovery time for the majority of unplanned failures.

  • Disaster avoidance

    With a stretched cluster, you can prevent service outages before an impending disaster.