VMware Cloud Foundation uses NFS storage for supplemental storage in the management domain. Supplemental storage is mainly used for extending the capacity of the management domain to host more VMs or storing auxiliary data like backups. However, it is not mandatory to have a supplemental storage if NFS storage is not available.

Figure 1. Logical Storage Design
The management ESXi hosts are also connected to an optional supplemental datastore for backup and logs and to host auxiliary VM storage. The supplemental datastore i smounted on NAS storage.