Fan Speed Critical / Cooling Redundancy Lost

A cooling fan hits a critical speed/fault or loses redundancy, leading to rising GPU temperatures and thermal throttling if not addressed.

Fan Speed Critical / Cooling Redundancy Lost is a Infrastructure failure seen during ML training runs. A cooling fan hits a critical speed/fault or loses redundancy, leading to rising GPU temperatures and thermal throttling if not addressed. Common tags: Fan, Cooling, Thermal, Ipmi.

Fan hardware failure or bearing wear. Blocked airflow / dust. Cooling redundancy lost. Taken together, these mechanisms explain why the failure is reproducible, why it tends to surface on specific workloads or scales, and why generic mitigation attempts often fall short without addressing the underlying cause.

• GPU temperatures climbing on a node
• Fan fault or critical-speed sensor alarm
• Throughput dropping from thermal throttle

• Air-cooled GPU servers
• Dense 8-GPU chassis
• Nodes with BMC fan telemetry

Use this checklist to test the hypothesis against a small reproduction. No single line proves the root cause, so preserve the preceding events and compare one variable at a time.

• ✓Reproduce the failure from a clean checkpoint/seed: the symptom must appear without warm-up state from a previous run.
• ✓Verified signal present: Fan Speed Critical (sensor)
• ✓Verified signal present: Fan redundancy lost
• ✓Verified signal present: Rising GPU temperature with a fan alarm
• ✓A targeted fix from the "How to fix it" section eliminates or substantially reduces the symptom within one validation pass.

Select the traceback or open the failed terminal, then run Denpex locally to see the initiating rank, collateral failures, exact fix, and verification command without uploading the log.

• Fan hardware failure or bearing wear
• Blocked airflow / dust
• Cooling redundancy lost