You can create a stretched cluster that spans two geographic locations (or sites). Stretched clusters enable you to extend the
vSAN datastore across two sites to use it as stretched storage. The stretched cluster continues to function if a failure or scheduled maintenance occurs at one site.
Introduction to Stretched Clusters Stretched clusters extend the vSAN cluster from a single site to two sites for a higher level of availability and intersite load balancing. Stretched clusters are typically deployed in environments where the distance between data centers is limited, such as metropolitan or campus environments.
Stretched Cluster Design Considerations Consider these guidelines when working with a vSAN stretched cluster.
Best Practices for Working with Stretched Clusters When working with vSAN stretched clusters, follow these recommendations for proper performance.
Network Design for Stretched Clusters All three sites in a stretched cluster communicate across the management network and across the vSAN network. The VMs in both data sites communicate across a common virtual machine network.
Configure vSAN Stretched Cluster Configure a vSAN cluster that stretches across two geographic locations or sites.
Change the Preferred Fault Domain You can configure the secondary site as the preferred site. The current preferred site becomes the secondary site.
Change the Witness Host You can change the witness host for a vSAN stretched cluster.
Deploying a vSAN Witness Appliance Specific vSAN configurations, such as a stretched cluster, require a witness host. Instead of using a dedicated physical ESXi host as a witness host, you can deploy the vSAN witness appliance. The appliance is a preconfigured virtual machine that runs ESXi and is distributed as an OVA file.
Configure Network Interface for Witness Traffic vSAN data traffic requires a low-latency, high-bandwidth link. Witness traffic can use a high-latency, low-bandwidth and routable link. To separate data traffic from witness traffic, you can configure a dedicated VMkernel network adapter for vSAN witness traffic.
Convert a Stretched Cluster to a Standard vSAN Cluster You can decommission a stretched cluster and convert it to a standard vSAN cluster.