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The vSAN Cluster That Cost $40,000 Too Much Because Someone Spec’d 100GbE for a 25GbE Workload
vSANESA (Express Storage Architecture) requires 25GbE networking minimum. It does not require 100GbE. But walk through any data center with a vSAN deployment and you will find at least one cluster where the networking budget consumed 30 percent more than necessary because the spec was written by someone who confused “minimum” con “recommended” E “recommended” con “we might need it later.” This guide covers the hardware decisions that make or break vSAN ESA TCO — from server selection to NVMe drive count to network switch configuration.
Server Selection: The Golden Ratio of NVMe Bays to Memory Channels
vSAN ESA replaces the disk group model (cache drive + capacity drives) with a storage pool where all NVMe drives contribute to a single distributed datastore. The key hardware constraint is no longer the cache-to-capacity ratio — it is the ratio of NVMe bays to memory channels. Each NVMe drive consumes CPU cycles for I/O processing. A server with 24 NVMe bays and 2x 12-core CPUs will be CPU-bound on storage I/O long before it is capacity-bound. The rule of thumb: 2-3 NVMe drives per physical CPU core for mixed workloads, 3-4 for read-heavy.
| server | NVMe Bays | Recommended CPU (per node) | Max Usable Capacity (RAID 5, 4 Nodes) | Best For |
|---|---|---|---|---|
| Dell R670 (1U, 20x E3.S) | Fino a 20 E3.S Gen5 | 2x Xeon 6 (56+ cores total recommended) | ~300 TB (20x 7.68TB x 4 nodes, RAID 5) | High-density 1U, colocation-optimized |
| Dell R760 (2U, 24x 2,5 pollici) | Fino a 24 NVMe U.2 | 2x Xeon Gold 6448Y (32C each) | ~360 TB (24x 7.68TB x 4 nodes, RAID 5) | Balanced density and expansion |
| xFusion2288H V7 (2U, 25x 2,5 pollici) | Fino a 28 Nvme | 2x Xeon Gold 6448Y (32C each) | ~420 TB (28x 7.68TB x 4 nodes, RAID 5) | Maximum storage density in 2U |
| xFusion 5288 V7 (4U, 44x 3,5 pollici) | Fino a 4 Nvme + 44 HDD SAS | 2x Xeon Gold 6430 (32C each) | Nvme: ~60 TB + HDD: ~700 TB | Mixed NVMe + capacity HDD (vSAN OSA-style) |
Rete: 25GbE Is the Minimum. Here Is When 100GbE Actually Makes Sense.
vSAN ESA requires a minimum of 25GbE networking for the vSAN traffic VMkernel port. The actual bandwidth requirement scales with the number of NVMe drives per node and the write workload intensity:
| NVMe Drives per Node | Typical Peak vSAN Traffic (per node, write-heavy) | Required Network | Recommended Adapter |
|---|---|---|---|
| 4-8 Nvme | ~8-12 Gbps | 25Trasportare (sufficient) | Intel E810-XXVDA2 (225GbE, RDMA-capable) |
| 12-16 Nvme | ~15-22 Gbps | 25Trasportare (near saturation on writes) | 225GbE (LACP active-active, or vSAN traffic on dedicated 25GbE port) |
| 20-28 Nvme | ~25-35 Gbps | 100GbE recommended (dual 25GbE aggregated may saturate) | Mellanox ConnectX-6 Dx (2x 100GbE) or 2x 25GbE in LACP |
For most 4-node clusters with 8-12 NVMe drives per node, dual 25GbE SFP28 adapters with one port dedicated to vSAN traffic and the second port for management and vMotion is the cost-optimal configuration. 100GbE becomes justified at 20+ NVMe drives per node or when the cluster is being designed for future expansion to all-NVMe 28-drive nodes.
Four-Node vSAN ESA Cluster Reference Design
| Componente | Selection | Quantità | Estimated Cost (per node) |
|---|---|---|---|
| server | Dell R760 (24NVMe da 2,5 pollici) | 4 nodes | $18,000 |
| processore | 2x Xeon Gold 6448Y (32 core, 250W) | 8 CPUs (2 per node) | $3,100 X 8 = $24,800 |
| Memoria | 512 GB (16X 32 GB DDR5-4800, 1DPC) | 2 TB total (64 DIMM) | $2,800 per node |
| Magazzinaggio | 12x Micron 7450 PRO 7.68TB NVMe per node (RAID 5, vSAN policy FTT=1) | 48 azionamenti (12 per node) | $5,200 per node (drives only) |
| Rete | 2x Intel E810-XXVDA2 (25GbE SFP28 per node) | 8 adapters (2 per node) | $400 per adapter |
| Witness Host | Dell R470 (1U, single-socket, 64 GB, 2X 480 GB NVMe boot) | 1 node | $3,500 |
| Switch | Dell PowerSwitch S5248F-ON (4825GbE + 8x 100GbE) | 1 switch (shared, 8 ports used for vSAN) | $8,000 (allocated cost) |
| Total (4-node cluster + witness) | $133,500 | ||
Usable capacity: approximately 184 tubercolosi (12x 7.68TB x 4 nodes, RAID 5 within vSAN, FTT=1 with RAID 5 erasure coding). Prestazione: ~2.4M read IOPS, ~960K write IOPS aggregate across 4 nodes.
vSAN ESA vs vSAN OSA — The Migration Decision
| Factor | OSA (Original Storage Architecture) | ESA (Express Storage Architecture) |
|---|---|---|
| Storage model | Disk groups: 1 cache SSD + 1-7 capacity drives | Storage pool: all NVMe drives contribute equally |
| Minimum drives per node | 2 (1 cache + 1 capacità) | 4 NVMe drives per node |
| RAID within vSAN | RAID 1 (mirroring) or RAID 5/6 (erasure coding, capacity drives only) | RAID 5 per object natively, RAID 6 for FTT=2 |
| Network minimum | 10Trasportare | 25Trasportare |
| Space efficiency (FTT=1, 4 nodes) | RAID 1: 50 percent usable. RAID 5: ~75 percent usable. | RAID 5 natively: ~75 percent usable, with inline compression (~1.6:1 typical, fino a 4:1) |
| Best for new deployments in 2026 | Hybrid HDD+SSD, budget-constrained, 10GbE infrastructure | All-NVMe, performance-oriented, greenfield deployments |
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