The VMware Validated Design for Remote Office and Branch Office (ROBO) uses a small set of common building blocks called pods.

Pod Architecture Characteristics

Pods can include different combinations of servers, storage equipment, and network equipment, and can be set up with varying levels of hardware redundancy and varying quality of components. Pods are connected to a network core that distributes data between them. A pod is not defined by any hard, physical properties, as it is a standard unit of connected elements within the SDDC network fabric.

A pod is a logical boundary of functionality for the SDDC platform. While each pod typically spans one rack, it is possible to aggregate multiple pods into a single rack or for a pod to span multiple racks. For all pods, homogeneity and ease of replication are important.

Pod to Rack Mapping

Pods are not mapped one-to-one to 19" data center racks. While a pod is an atomic unit of a repeatable building block, a rack is merely a unit of size. Because pods can have different sizes, how pods are mapped to 19" data center racks depends on the use case. 

Note:

The consolidated pod cannot span racks. This is due to NSX controllers and other virtual machines on a VLAN backed network migrating to a different rack, where that IP subnet is not available due to layer 2 termination at the Top of Rack switch.