The approximate expected usable capacity is 40 TB. The cluster contains six hosts, each with two 4 TB NVMe disks, giving 48 TB of raw capacity. Because the policy uses FTT=1 with RAID-5 erasure coding, vSAN provides better capacity efficiency than mirroring. RAID-5 with FTT=1 typically uses approximately 1.33x overhead, leaving roughly 75% of raw capacity before additional reserves and data-reduction assumptions. The design also requires Host Rebuild Reservation, which reserves enough capacity to rebuild data after a host failure, and an Operational Reserve of 10% to support internal operations such as resynchronization and policy changes. The expected filesystem and object overhead of 25% further reduces available capacity, while the deduplication/compression ratio of 2 increases the effective usable capacity. After accounting for protection overhead, capacity reserves, operational overhead, and the stated data-reduction assumption, the closest expected usable value from the available choices is 40 TB. Reference topics: vSAN Capacity Sizing, RAID-5 Erasure Coding, Deduplication and Compression, Host Rebuild Reserve, Operational Reserve.

NFS must be used as principal storage because the hosts have no local storage available. vSAN OSA and vSAN ESA both require local storage devices on the ESX hosts to create the vSAN datastore, so neither can be selected as principal storage in this design. NVMe over RDMA is supported as a high- performance NVMe over Fabrics transport in vSphere, but in the VCF storage model it is treated as supplemental storage rather than principal storage for workload domain creation. Therefore, NVMe over RDMA cannot be the initial principal datastore used to build the Workload Domain. NFS is the valid principal storage option from the provided choices, and after the Workload Domain is created, NVMe over RDMA can be added as supplemental storage for additional performance or capacity use cases. This build order satisfies the lack of local disks, uses a supported principal storage type, and allows the NVMe over RDMA design requirement to be met after the domain exists. Reference topics:
Principal Storage, Supplemental Storage, NFS Storage Model, NVMe over RDMA, VCF Workload Domain Storage Design.