Glossary3 sections1 min read
What is InfiniBand?
InfiniBand is a high-bandwidth, low-latency network fabric used to connect servers in high-performance computing and multi-node GPU training clusters. It supports RDMA, so network cards can move data directly between machines' memory, including GPU memory with GPUDirect RDMA.
Why it matters when renting a GPU
Inside one server, GPUs talk over NVLink; between servers, they talk over the network. Multi-node training needs a fast fabric such as InfiniBand.
For single-node jobs, the network between servers matters little; for multi-node training, ask about the fabric and its speed per GPU.
Worked example
A 400 Gb/s InfiniBand port carries 400 ÷ 8 = 50 GB/s per direction, while the H100 SXM lists NVLink 4 (900 GB/s) between GPUs inside a server: that gap is why models are split to keep the heaviest traffic within a node.
Frequently asked questions
- Do I need InfiniBand for one GPU?
- No. InfiniBand matters when a job spans several servers.