InfiniBand vs Ethernet for GPU Clusters: Which to Choose in India?
Compare InfiniBand and Ethernet networking for GPU clusters used in AI training. Bandwidth, latency, RDMA, and cost analysis for Indian data centres.
| Spec | InfiniBand (NVIDIA ConnectX-7 / NDR 400G) | Ethernet (100GbE / 400GbE with RoCE) |
|---|---|---|
| bandwidth | 400 Gbps per port (NDR), 200 Gbps (HDR) | 100-400 Gbps per port |
| latency | Sub-microsecond (0.5-1.0 us) | 2-5 microseconds (with RoCE v2) |
| rdma | Native RDMA support via InfiniBand Verbs, GPUDirect RDMA | RDMA over Converged Ethernet (RoCE v2): requires lossless configuration |
| cost | High. INR 1.5-4 lakh per HCA + InfiniBand switch (INR 15-50 lakh) | Moderate. INR 30,000-1.5 lakh per NIC + standard Ethernet switches |
| complexity | Requires InfiniBand expertise, Subnet Manager, specialised cabling | Familiar technology, but lossless configuration for RoCE adds complexity |
Best for Performance
InfiniBand (NVIDIA ConnectX-7 / NDR 400G)
Best for Value
Ethernet (100GbE / 400GbE with RoCE)
Choose InfiniBand (NVIDIA ConnectX-7 / NDR 400G) if...
You are building large-scale GPU training clusters (32+ GPUs), need to minimise inter-node communication latency for distributed training (data parallelism, model parallelism), or are running NCCL-based multi-node training. InfiniBand delivers 30-40% better multi-node training throughput compared to Ethernet for large models.
Choose Ethernet (100GbE / 400GbE with RoCE) if...
You are building smaller GPU clusters (up to 16-32 GPUs), primarily running inference workloads, want to use existing Ethernet infrastructure, or need to converge storage and compute networking. RoCE v2 over 100GbE is sufficient for many inference and moderate training workloads.
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Frequently Asked Questions
Do I need InfiniBand for LLM training in India?
For large-scale training across 8+ nodes (32+ GPUs), InfiniBand provides a meaningful performance advantage due to its lower latency and native RDMA. For fine-tuning or training smaller models on a single 8-GPU node, InfiniBand is not necessary. The choice depends on your cluster scale and model size.
Is InfiniBand available and supportable in India?
Yes. NVIDIA Mellanox InfiniBand equipment is available through authorised distributors in India. However, finding InfiniBand-experienced network engineers can be challenging. RawCompute provides InfiniBand cluster design and deployment services with trained engineers.
Can I use RoCE as a cheaper alternative to InfiniBand?
RoCE v2 over 100GbE or 400GbE is a viable alternative for smaller clusters. It requires careful network configuration (PFC, ECN for lossless operation) but avoids the cost of InfiniBand switches. For clusters up to 16 GPUs, RoCE performance is typically within 10-15% of InfiniBand.
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