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How Meta trains large language models at scale

Engineering at Meta

There are two leading choices in the industry that fit these requirements: RoCE and InfiniBand fabrics. On the other hand, Meta had built research clusters with InfiniBand as large as 16K GPUs. So we decided to build both: two 24k clusters , one with RoCE and another with InfiniBand. Both of these options had tradeoffs.

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A RoCE network for distributed AI training at scale

Engineering at Meta

Topology We built a dedicated backend network specifically for distributed training. To support large language models (LLMs), we expanded the backend network towards the DC-scale, e.g., incorporating topology-awareness into the training job scheduler. We designed a two-stage Clos topology for AI racks, known as an AI Zone.

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Building Meta’s GenAI Infrastructure

Engineering at Meta

The other cluster features an NVIDIA Quantum2 InfiniBand fabric. Through careful co-design of the network, software, and model architectures, we have successfully used both RoCE and InfiniBand clusters for large, GenAI workloads (including our ongoing training of Llama 3 on our RoCE cluster) without any network bottlenecks.