An architect has been tasked with designing a vSAN OSA storage solution for a VMware...

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.