Maximizing the Power of NVIDIA GB300 NVL72: NVLink Domain-Aware Placement Groups in Ray

Ray has introduced NVLink Domain-Aware Placement Groups to improve scheduling on NVIDIA GB200 and GB300 NVL72 rack-scale systems, which connect 72 Blackwell GPUs and 36 Grace CPUs through a high-bandwidth NVLink fabric. The feature enables users to require related Ray actors and resource bundles to be colocated within one NVLink Domain, typically a rack, rather than being distributed across nodes or racks as with earlier node-focused placement policies. This topology awareness can improve collective communication performance by keeping GPU-intensive operations such as all-reduce on NVLink, while also preserving placement intent during node failures or maintenance by seeking replacement capacity within the same domain. In NVIDIA GEAR’s 512-GPU vision-language-action training evaluation, domain-aware placement organized 64-GPU groups within individual NVLink Domains and delivered 1.13 times faster iterations than a less localized deployment. The approach may also benefit disaggregated inference, where prefill and decode workers exchange cache data, and reinforcement learning pipelines with tightly coupled training components. Planned extensions include additional placement strategies such as spreading workloads across racks, support for hierarchical infrastructure topologies, and improved visibility into GPU locality.

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