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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” と “recommended” と “recommended” と “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.
| サーバ | NVMe Bays | Recommended CPU (per node) | Max Usable Capacity (レイド 5, 4 Nodes) | Best For |
|---|---|---|---|---|
| Dell R670 (1う, 20x E3.S) | まで 20 E3.S Gen5 | 2x Xeon 6 (56+ cores total recommended) | ~300 TB (20x 7.68TB x 4 nodes, レイド 5) | High-density 1U, colocation-optimized |
| Dell R760 (2う, 24× 2.5インチ) | まで 24 NVMe U.2 | 2x Xeon Gold 6448Y (32C each) | ~360 TB (24x 7.68TB x 4 nodes, レイド 5) | Balanced density and expansion |
| xFusion 2288H V7 (2う, 25× 2.5インチ) | まで 28 NVMe | 2x Xeon Gold 6448Y (32C each) | ~420 TB (28x 7.68TB x 4 nodes, レイド 5) | Maximum storage density in 2U |
| xフュージョン 5288 V7 (4う, 44× 3.5インチ) | まで 4 NVMe + 44 SAS HDD | 2x Xeon Gold 6430 (32C each) | NVMe: ~60 TB + HDD: ~700 TB | Mixed NVMe + capacity HDD (vSAN OSA-style) |
ネットワーキング: 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 | 25運ぶ (sufficient) | インテル E810-XXVDA2 (2× 25GbE, RDMA-capable) |
| 12-16 NVMe | ~15-22 Gbps | 25運ぶ (near saturation on writes) | 2× 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
| 成分 | Selection | Quantity | Estimated Cost (per node) |
|---|---|---|---|
| サーバ | Dell R760 (24× 2.5 インチ NVMe) | 4 nodes | $18,000 |
| CPU | 2x Xeon Gold 6448Y (32 コア, 250W) | 8 CPUs (2 per node) | $3,100 バツ 8 = $24,800 |
| メモリー | 512 GB (16バツ 32 GB DDR5-4800, 1DPC) | 2 TB total (64 DIMM) | $2,800 per node |
| 保管所 | 12x Micron 7450 PRO 7.68TB NVMe per node (レイド 5, vSAN policy FTT=1) | 48 ドライブ (12 per node) | $5,200 per node (drives only) |
| ネットワーキング | 2x Intel E810-XXVDA2 (25GbE SFP28 per node) | 8 アダプター (2 per node) | $400 per adapter |
| Witness Host | Dell R470 (1う, single-socket, 64 GB, 2バツ 480 GB NVMe boot) | 1 node | $3,500 |
| Switch | デル パワースイッチ S5248F-ON (48× 25GbE + 8x 100GbE) | 1 スイッチ (shared, 8 ports used for vSAN) | $8,000 (allocated cost) |
| Total (4-node cluster + witness) | $133,500 | ||
Usable capacity: approximately 184 結核 (12x 7.68TB x 4 nodes, レイド 5 within vSAN, FTT=1 with RAID 5 erasure coding). パフォーマンス: ~2.4M read IOPS, ~960K write IOPS aggregate across 4 nodes.
vSAN ESA vs vSAN OSA — The Migration Decision
| 要素 | 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 容量) | 4 NVMe drives per node |
| RAID within vSAN | レイド 1 (mirroring) or RAID 5/6 (erasure coding, capacity drives only) | レイド 5 per object natively, レイド 6 for FTT=2 |
| Network minimum | 10運ぶ | 25運ぶ |
| Space efficiency (FTT=1, 4 nodes) | レイド 1: 50 percent usable. レイド 5: ~75 percent usable. | レイド 5 natively: ~75 percent usable, with inline compression (~1.6:1 typical, まで 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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