Configure a stretched cluster

Perform this task to configure a stretched cluster that spans two geographic locations (sites) for disaster recovery upon failure of one site. Stretched clusters are typically deployed in metropolitan environments. In a stretched cluster configuration, both sites are active sites.

After you enable stretched cluster configuration and add hosts to the stretched regions, the system will create the following groups and rules automatically:

Stretched host groups with a name of "cluster name_Host Group in Local Region" and "cluster name_Host Group in Remote Region"
Stretched VM groups with a name of "cluster name_VM Group in Local Region" and "cluster name_VM Group in Remote Region"

If a host does not have any VMs running on it, the system also creates a VM group, and automatically adds VMs to the VM group when VMs are added to the host later.
VM-host affinity rules of the Should Run on Hosts in This Group type and with a name of "cluster name_VM-Host Affinity Rule in Local Region" and "cluster name_ VM-Host Affinity Rule in Remote Region"

In case of automatic VM migration triggered by HA or DRS, the system selects a destination host in the following sequence:

Failover hosts configured:
- Failover host in the stretched region where the attached host of the VM belongs.
- Failover host in the other stretched region. After VM migration, you can select to have the VM stay in the current stretched region or move it to its preferred stretched region as long as a host operating correctly exists in that region.
Failover hosts not configured:
- Another host in the stretched region where the attached host of the VM belongs.
- Host in the other stretched region. After VM migration, you can select to have the VM stay in the current stretched region or move it to its preferred stretched region as long as a host operating correctly exists in that region.

Restrictions and guidelines

Before configuring a stretched cluster, delete VM-host affinity rules that conflict with VM-host affinity rules with a name of "cluster name_VM-Host Affinity Rule in Local Region" or "cluster name_VM-Host Affinity Rule in Remote Region".
If you enable stretched cluster configuration, you must add your hosts to the cluster local region and cluster remote region.
As a best practice, add hosts in a local site to the cluster local region, and add hosts in a remote site to the cluster remote region.

Enable or disable stretched cluster configuration

On the top navigation bar, click Compute.
From the left navigation pane, select Resource Navigation > All > Resources > Host Pool Name > Cluster Name.
Click More, and then select Stretched Cluster.
Enable or disable stretched cluster configuration. If you enable stretched cluster configuration, you must add hosts to the cluster local region and cluster remote region.
Click OK.

Add hosts to the cluster local region and cluster remote region

On the top navigation bar, click Compute.
From the left navigation pane, select Resource Navigation > All > Resources > Host Pool Name > Cluster Name.
Click More, and then select Stretched Cluster.
Add hosts to the cluster local region and cluster remote region as needed. If a large number of hosts exist in a cluster, you can enter host names to filter hosts.
Click OK.

Parameters

Stretched Cluster: Enable or disable stretched cluster configuration.
- If you enable this feature, you must configure hosts in the cluster local region and cluster remote region. After configuration, the system automatically creates corresponding host groups, VM groups, and affinity rules.
- If you disable this feature, the system will delete corresponding host groups, VM groups, and affinity rules.
Cluster Local Region: Add hosts to the cluster local region.
Cluster Remote Region: Add hosts to the cluster remote region.

Hosts within a cluster must be in either the cluster local region or the cluster remote region.