This procedure describes how to stretch a cluster across two availability zones.

As an example, we will follow a use case with two availability zones in two buildings in an office campus - AZ1 and AZ2. Each availability zone has its own power supply and network. The management domain is on AZ1 and contains the default cluster, SDDC-Cluster1. This cluster contains four ESXi hosts. AZ1 also contains the default bring-up pool, bringup-networkpool.
vSAN network VLANID=1613
IP range= -
vMotion network VLANID=1612
IP range= -

There are four ESXi hosts in AZ2 that are not in the Cloud Foundation inventory yet.

We will stretch the default cluster SDDC-Cluster1 in the management domain from AZ1 to AZ2.

Figure 1. Stretch Cluster Example


Ensure you have completed the steps listed in Prerequisites for Stretching a Cluster.


  1. Create a network pool, AZ2-networkpool, on AZ2. See Create a Network Pool.
    Based on our example, here are the network details for the network pool.
    vSAN network VLANID=1613
    IP range= -
    vMotion network VLANID=1612
    IP range= -
  2. Commission the four hosts in AZ2 and associate them with AZ2-networkpool. In our example, these are,,,
  3. Retrieve the FQDNs of the hosts in AZ2.
    1. On the SDDC Manager Dashboard, click Hosts.
    2. Note down the FQDNs for the hosts in AZ2.
  4. SSH in to the SDDC Manager VM using the vcf administrative user account.
  5. Enter su to switch to the root user and navigate to the /opt/vmware/sddc-support directory.
  6. Enter the following command:
    ./sos --stretch-vsan --sc-domain <DOMAIN NAME> --sc-cluster <CLUSTER NAME> --sc-hosts <HOSTFQDN,HOSTDQND2,...> --witness-host-fqdn <WITNESS HOST FQDN> --witness-vsan-ip <WITNESS VSAN IP> --witness-vsan-cidr <WITNESS VSAN CIDR> --esxi-license-key <LICENSE KEY>
    Example input and response:
    root@sddc-manager [ /opt/vmware/sddc-support ]# ./sos --stretch-vsan --sc-domain MGMT --sc-cluster SDDC-Cluster1 --sc-hosts esxi-5.vrack.vsphere.local,esxi-6.vrack.vsphere.local --witness-host-fqdn esxi-11.vrack.vsphere.local --witness-vsan-ip --witness-vsan-cidr --esxi-license-key AAAAA-BBBBB-CCCCC-DDDDD-EEEEE
    Welcome to Supportability and Serviceability(SoS) utility!
    Logs : /var/log/vmware/vcf/sddc-support/stretchCluster-2019-02-13-08-51-34-12479
    Stretch Cluster operation log : /var/log/vmware/vcf/sddc-support/stretchCluster-2019-02-13-08-51-34-12479/sos.log
    Starting vSAN stretched cluster operations..
    Api Response:{
      "taskId": "d670ff00-24a3-4739-b5ff-b5317d709f36",
      "resourceId": "0f8d112d-aa3f-4ca8-a8bd-b95e0e1ea2f5",
      "resourceType": "ESXI",
      "state": "IN_PROGRESS",
      "description": "Stretch vSAN Cluster - SDDC-Cluster1 in VMware Cloud Foundation",
      "timestamp": 1550047894872,
      "id": "d670ff00-24a3-4739-b5ff-b5317d709f36"
  7. Monitor the state of the task in the SDDC Manager Dashboard.
  8. When the task completes successfully, validate that stretched cluster operations are working correctly by logging in to the vSphere Web Client.
    The time it takes to complete a policy compliance check depends on the number of VMs in the clsuter.
    1. Check the vSAN Health page.
      1. On the home page, click Host and Clusters and then select the stretched cluster (SDDC-Cluster1 in our example).
      2. Click Monitor > vSAN > Health.
      3. Click Retest.
      4. Fix errors, if any.
    2. Check the vSAN Storage Policy page.
      1. On the home page, click Policies and Profiles > VM Storage Policies > vSAN Default Storage Policies .
      2. Select the policy associated with the vCenter Server for the stretched cluster.
      3. Click Monitor > VMs and Virtual Disks.
      4. Click Refresh.
      5. Click Trigger VM storage policy compliance check .
      6. Check the Compliance Status column for each VM component.
      7. Fix errors, if any.

What to do next

It is recommended that you add new VMs to the primary AZ and associate the host rule for the new VM with the primary AZ rule.