The SDDC functionality is distributed across multiple workload domains and VMware vSphere® clusters. A workload domain, whether it is a management or virtual infrastructure domain, is a logical abstraction of compute, storage and network capacity and can consist of one or more clusters. Each cluster can exist vertically in a single rack or be spanned horizontally across multiple racks. You determine the total number of racks for each cluster type according to your scalability needs.

VI workload domains are provisioned automatically by SDDC Manager and administered and patched independently.

Virtual Infrastructure Workload Domain to Rack Mapping

The relationship between VI workload domains and data center racks is not one-to-one. While a workload domain is an atomic unit of repeatable building blocks, a rack is a unit of size. Because workload domains can have different sizes, you map VI workload domains to data center racks according to your requirements and physical infrastructure constraints.

VI workload domain clusters can be deployed in one rack or span multiple racks. You can also deploy each VI workload domain cluster in a rack with 1:1 mapping.

vSphere clusters in the VI workload domains host the VMware NSX® Edge™ clusters needed to service north-south traffic of your workloads. When using a Layer 3 network fabric, NSX Edge clusters cannot be deployed on clusters spanning multiple racks. NSX Edge appliances rely on VLAN-backed networks for management and uplink connectivity. The physical network configuration terminates Layer 2 networks in each rack at the top-of-rack (ToR) switch. Therefore, you cannot migrate an NSX Edge appliance to a different rack because the IP subnet is available only in the rack where the virtual machine currently runs.

Table 1. Virtual Infrastructure Workload Domain to Rack Configuration Options

VI Workload Domain to Rack Configuration


VI workload domain in one rack

A VI workload domain can occupy exactly one rack.

Multiple VI workload domains in one rack

Two or more VI workload domains can be placed in a single rack.

VI workload domain across multiple racks

A VI workload domain can span multiple adjacent racks. If you are using a Layer 3 network fabric, NSX Edge clusters cannot be hosted on stretched clusters.

Figure 1. VI Workload Domain in One Rack
Figure 2. VI Workload Domain Spanning Multiple Racks

Figure 3. VI Workload Domain with Multiple Availability Zones Spanning Multiple Racks