Prerequisites for Stretching a Cluster

This section lists the prerequisites for preparing the cluster for stretching.

• Download the Deployment for Multiple Availability Zones document and read it to understand the requirements.
• Ensure that you have a vSAN Enterprise license, which is required for stretching a cluster.
• All VMs on an external network must be on a virtual wire. If they are on a VLAN, that VLAN must be stretched.
• Each stretched cluster requires a vSAN witness host in a third party location. The maximum RTT on the witness is 200ms.
• The witness host should be running the same version of ESXi as the ESXi hosts in the stretched cluster. To upgrade ESXi on the witness host, use vSphere Update Manager.
• If you are stretching a cluster in a VI workload domain, you must stretch the management domain cluster first. vCenter Servers for all workload domains are in the management domain. Hence, you must protect the management domain to ensure that you can access and manage the workload domains.
• Ensure that you have enough hosts such that there is an equal number of hosts on each availability zone. This is to ensure that there are sufficient resources in case an availability zone goes down completely.
• The TCP port and the UDP ports needs to be open for witness traffic between the witness host and the vSAN cluster data nodes. See KB article 52959.

Note: You cannot deploy a PKS solution on a stretched cluster.