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1. IL-0126 The OPT-175B training run restarted more than 40 times in two weeks as cloud GPU nodes failed with ECC errors, replacement nodes came back faulty, and checkpoint downloads hung

   Meta AI2021

   Symptoms

   Between the team's 17 November 2021 update and 3 December 2021, the 175B-parameter OPT training run went down and had to be restarted more than 40 times, for hardware, infrastructure and training stability reasons. A hardware fault could stop the run for hours at any time of day, and several did over the Thanksgiving break.

   Training job failureGPU unavailable

   Trigger

   Nodes in the cloud training cluster failed with ECC errors, and each failure took the training run down.

   Root cause

   Dependency failure

   Component

   GPU hardware and memoryNCCLInfiniBand fabricObject storage

   Contributing factor

   No headroomLimited debug accessNo runbook

   Detection

   During these two weeks the team added monitoring of train.log, GPU burn-in testing to detect memory errors, and automated InfiniBand testing.

   Remediation

   • replaced failed nodes, and later did it through a script
   • added GPU burn-in testing to detect memory errors
   • automated InfiniBand testing
   • added monitoring of train.log
   • debugged the cloud provider's Python API until checkpoint downloads from the blob store worked well enough

   Action items

   • Run an on-call rotation for the training run, with runbooks and tooling for the most common issues, and invite more people to join it

   Lessons

   At this scale cloud hardware failures are certain, and the team concluded that automating the handling of hardware failures is necessary. Without spare nodes and burn-in tests, each failure costs hours and a replacement can bring the same fault back. The team also concluded that cloud infrastructure instability is something to always prepare for, because the customer has no control over the underlying hardware. A checkpoint large enough to need hundreds of multi-gigabyte downloads makes the storage path part of recovery time.

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