Question 410
An engineer observes: A node experiences intermittent network errors only during peak HPL and NCCL workload overlap, and the team assumes it is a faulty transceiver. Which underlying mechanism is most relevant?
Explanation
Correct Answer
The operational evidence follows from the mechanism that Power transients and shared-resource pressure can manifest as network instability under simultaneous load. Address it by Review PSU, board power and shared resource telemetry alongside optical errors during combined stress; then test whether A synchronized stress test after the identified power fix has no fabric errors or voltage excursions.
Incorrect Answers
This alternative addresses the separate case “The operator sees repeated training slowdowns after a rack cooling change but assumes the NCCL library is defective”. The key distinction is that Thermal throttling can reduce compute progress and create collective stragglers without an NCCL defect. The deciding requirement here is “Power transients and shared-resource pressure can manifest as network instability under simultaneous load”.
The option would apply to “A training node reports intermittent GPU Xid faults during collective operations but its nvidia-smi inventory remains normal”. The operational evidence follows from the mechanism that A GPU can enumerate normally while intermittent compute or memory faults occur under particular workloads. This question instead requires “Power transients and shared-resource pressure can manifest as network instability under simultaneous load”.
The related but distinct situation is “A multi-GPU server repeatedly loses one NIC link when its fan tray slows under load”. The controlling explanation is that Cooling failures can indirectly destabilize network or accelerator components exposed to excess heat. For the stated problem, “Power transients and shared-resource pressure can manifest as network instability under simultaneous load” addresses the central condition.