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System DesignMedium· Distributed Training· Scaling Laws· Data Parallelism

Why can’t you just scale data parallelism to 10,000 GPUs?

Scaling data parallelism (DP) indefinitely is limited by memory and efficiency constraints. Without ZeRO-3, DP does not reduce the memory footprint of parameters per GPU. Additionally, there is a critical batch size beyond which adding more replicas does not improve sample efficiency, meaning you run out of a useful batch-size budget before you run out of hardware. At very high DP degrees, the synchronization overhead of ZeRO-3 and topology-dependent latency across spine switches create performance degradation.

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