The vSAN Cluster That Cost $40,000 Too Much Because Someone Spec’d 100GbE for a 25GbE Workload
vSAN ESA (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” مع “recommended” و “recommended” مع “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.
| الخادم | NVMe Bays | Recommended CPU (per node) | Max Usable Capacity (غارة 5, 4 Nodes) | Best For |
|---|---|---|---|---|
| Dell R670 (1يو, 20x E3.S) | يصل إلى 20 E3.S Gen5 | 2x Xeon 6 (56+ cores total recommended) | ~300 TB (20x 7.68TB x 4 nodes, غارة 5) | High-density 1U, colocation-optimized |
| Dell R760 (2يو, 24× 2.5 بوصة) | يصل إلى 24 NVMe U.2 | 2x Xeon Gold 6448Y (32C each) | ~360 TB (24x 7.68TB x 4 nodes, غارة 5) | Balanced density and expansion |
| xFusion 2288H V7 (2يو, 25× 2.5 بوصة) | يصل إلى 28 NVME | 2x Xeon Gold 6448Y (32C each) | ~420 TB (28x 7.68TB x 4 nodes, غارة 5) | Maximum storage density in 2U |
| xFusion 5288 V7 (4يو, 44x 3.5-inch) | يصل إلى 4 NVME + 44 SAS HDD | 2x Xeon Gold 6430 (32C each) | NVME: ~60 TB + HDD: ~700 TB | Mixed NVMe + capacity HDD (vSAN OSA-style) |
Networking: 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 | 25يحمل (sufficient) | Intel E810-XXVDA2 (2x 25GbE, RDMA-capable) |
| 12-16 NVME | ~15-22 Gbps | 25يحمل (near saturation on writes) | 2x 25GbE (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
| عنصر | Selection | Quantity | Estimated Cost (per node) |
|---|---|---|---|
| الخادم | Dell R760 (24x 2.5-inch NVMe) | 4 nodes | $18,000 |
| وحدة المعالجة المركزية | 2x Xeon Gold 6448Y (32 النوى, 250دبليو) | 8 CPUs (2 per node) | $3,100 x 8 = $24,800 |
| ذاكرة | 512 غيغابايت (16x 32 GB DDR5-4800, 1DPC) | 2 TB total (64 وحدات ذاكرة DIMM) | $2,800 per node |
| تخزين | 12x Micron 7450 PRO 7.68TB NVMe per node (غارة 5, vSAN policy FTT=1) | 48 محركات (12 per node) | $5,200 per node (drives only) |
| Networking | 2x Intel E810-XXVDA2 (25GbE SFP28 per node) | 8 محولات (2 per node) | $400 per adapter |
| Witness Host | Dell R470 (1يو, single-socket, 64 غيغابايت, 2x 480 GB NVMe boot) | 1 node | $3,500 |
| Switch | Dell PowerSwitch S5248F-ON (48x 25GbE + 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 تيرابايت (12x 7.68TB x 4 nodes, غارة 5 within vSAN, FTT=1 with RAID 5 erasure coding). أداء: ~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 سعة) | 4 NVMe drives per node |
| RAID within vSAN | غارة 1 (mirroring) or RAID 5/6 (erasure coding, capacity drives only) | غارة 5 per object natively, غارة 6 for FTT=2 |
| Network minimum | 10يحمل | 25يحمل |
| Space efficiency (FTT=1, 4 nodes) | غارة 1: 50 percent usable. غارة 5: ~75 percent usable. | غارة 5 natively: ~75 percent usable, with inline compression (~1.6:1 typical, يصل إلى 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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