What does this failure look like in production?

In production this failure typically appears during the first tens-to-hundreds of training steps: loss curves become non-monotonic, validation metrics plateau above the baseline, and downstream checkpoints either diverge or fail to improve. Engineers frequently misread it as data drift when the underlying mechanism is shard files were created in /tmp then atomically moved to the cache directory; /tmp and cache sat on different mount points. Validating against the symptom list in this entry is the fastest way to confirm the diagnosis.

Is this a hardware or a software issue?

Infrastructure failures can look like either layer depending on the symptom. The discriminator is the resolution of the symptom to the recommended fix: if applying the steps under "How to fix it" eliminates the symptom, this is a software/configuration class issue regardless of the hardware it surfaced on. Repeat the fix on a fresh node to confirm.

How long does the fix typically take?

Most resolutions from this entry take 10 to 30 minutes of engineer time once the diagnosis is confirmed. Long fixes come from skipping the diagnosis step and chasing apparent symptoms (validation drift, memory growth, slow throughput) instead of the actual root cause listed above. Apply the fix in a small experiment first, then roll it forward.

Does this affect inference or only training?

Primarily this is a infrastructure failure observed during training, but the same misconfiguration can leak into downstream evaluation and serving. Treat the prevention checklist as a guardrail: any pipeline that touches a trained checkpoint should re-validate the failure mode before promoting the model.

What's the cheapest way to confirm this is the problem?

Cheapest signal: reproduce the symptom on a 1-GPU toy run with the same configuration. If the toy run exhibits the same behavior, the cause is the configuration rather than the cluster. If only the multi-GPU run is affected, the failure is a distributed interaction, so Background data migration workers writing to diverse mount points is the most likely layer to inspect.

Can the Denpex platform detect this automatically?

Yes. Denpex correlates the symptoms in this entry against your training logs in real time and surfaces the failure taxonomy, root cause, and exact remediation command on the console. Three full diagnoses are included free during signup, and the encyclopedia entry you are reading is generated from the same signal library that powers the platform.

What related failures should I check next?

Closely related failures cluster around #huggingface, #xet, #storage-migration. After applying this fix, validate against the related entries below to confirm no overlapping cause is masking as this one. Engineers routinely discover that the dominant failure mode is actually a second, sibling failure compounded on top.

Will this recur after the fix?

Applied once with the prevention checklist, this failure does not recur under normal operation. The recurring variant most engineers encounter is the re-emergence of the same symptom on a different model or stack after huggingface is upgraded. Pin compatible versions and rerun the prevention smoke test on every dependency change.

Is there a fingerprint I can monitor?

Yes. Pod disk usage at 100% with `df -h` showing /tmp filesystem full is the highest-signal fingerprint. Wire a metric or alert on that signal (or its absence after the fix) so you can detect the recurrence automatically. The Denpex platform encodes this exact fingerprint and surfaces it directly in the dashboard.

What is the official documentation that covers this?

Reference documentation is listed in the References section at the bottom of this entry. The most authoritative URLs are the upstream framework docs and the issue trackers cited; the Denpex entry synthesizes both into the executive, engineer, and on-call perspectives so each audience can act without reading every linked source.

Does this entry include working code?

Yes. The "Code Examples" section contains copy-paste-ready snippets that target the most common stacks (PyTorch, Hugging Face Trainer, DeepSpeed, Megatron-LM, vLLM/Transformers). Each snippet is annotated with why it works so you can adapt the pattern to your own framework without losing fidelity.

Xet Storage Migration Workers Filling Disk with Orphaned Temporary Shard Files

Q: How does this scale from 1 GPU to 1000 GPUs?

At single-GPU scale the symptom usually looks like slow convergence or a single anomalous loss value. At 64+ GPU scale, distributed interactions amplify shard files were created in /tmp then atomically moved to the cache directory; /tmp and cache sat on different mount points through collectives, and the failure can manifest as a full job abort. Always reproduce the fix at the smallest cluster configuration that still exhibits the symptom before promoting to production scale.

During HuggingFace's migration from Git LFS to Xet storage backend, migration worker pods filled their ephemeral disks with orphaned temporary shard files. The shard files were first written to /tmp and then moved to the Xet cache, but /tmp and the cache were on different mount points. The move failed silently, orphan shard files were never cleaned up, and the disk eventually filled, triggering No space left on device errors across the migration fleet.

Quick answer

During HuggingFace's migration from Git LFS to Xet storage backend, migration worker pods filled their ephemeral disks with orphaned temporary shard files.

Symptom: Migration workers report "No space left on device" errors
Root cause: Shard files were created in /tmp then atomically moved to the cache directory; /tmp and cache sat on different mount points. Cross-filesystem `rename()` silently fails (EXDEV error), falling back to copy+delete which was not implemented in the worker. Orphaned shard files accumulated in /tmp until disk exhaustion; no cleanup mechanism existed for failed temp files.
Recommended fix: rename()
How Denpex helps: Denpex investigates Xet Storage Migration Workers Filling Disk with Orphaned Temporary Shard Files using the evidence you provide or your connected workload collects. Earlier rank, host or application evidence is needed to distinguish an initiating failure from a downstream report.

Infrastructure#huggingface#xet#storage-migration#disk-pressure#tmp-file#orphaned-files

What this failure is

Xet Storage Migration Workers Filling Disk with Orphaned Temporary Shard Files is a Infrastructure failure seen during ML training runs. During HuggingFace's migration from Git LFS to Xet storage backend, migration worker pods filled their ephemeral disks with orphaned temporary shard files. The shard files were first written to /tmp and then moved to the Xet cache, but /tmp and the cache were on different mount points. The move failed silently, orphan shard files were never cleaned up, and the disk eventually filled, triggering No space left on device errors across the migration fleet. Common tags: Huggingface, Xet, Storage Migration, Disk Pressure.

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Why it happens (the mechanism)

Shard files were created in /tmp then atomically moved to the cache directory; /tmp and cache sat on different mount points. Cross-filesystem `rename()` silently fails (EXDEV error), falling back to copy+delete which was not implemented in the worker. Orphaned shard files accumulated in /tmp until disk exhaustion; no cleanup mechanism existed for failed temp files. 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.

What you'll observe

Migration workers report "No space left on device" errors
Disk usage on worker pods grows monotonically and never decreases
Migration throughput drops to zero as workers cannot write new shard files

Common symptoms and what they mean

Symptom	Why it happens
Pod disk usage at 100% with `df -h` showing /tmp filesystem full	Shard files were created in /tmp then atomically moved to the cache directory; /tmp and cache sat on different mount points
Large temporary files remaining in /tmp directory that were intended to be moved to cache mount	Cross-filesystem `rename()` silently fails (EXDEV error), falling back to copy+delete which was not implemented in the worker
Profiling shows pods are network and EBS I/O bottlenecked despite apparent CPU capacity	Orphaned shard files accumulated in /tmp until disk exhaustion; no cleanup mechanism existed for failed temp files

Which systems are affected

Background data migration workers writing to diverse mount points
Kubernetes pods with separate ephemeral and persistent volume mounts
Storage backends with atomic move operations spanning filesystem boundaries

How to confirm this is the problem

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: Pod disk usage at 100% with `df -h` showing /tmp filesystem full
✓Verified signal present: Large temporary files remaining in /tmp directory that were intended to be moved to cache mount
✓Verified signal present: Profiling shows pods are network and EBS I/O bottlenecked despite apparent CPU capacity
✓A targeted fix from the "How to fix it" section eliminates or substantially reduces the symptom within one validation pass.

Root cause

Shard files were created in /tmp then atomically moved to the cache directory; /tmp and cache sat on different mount points
Cross-filesystem `rename()` silently fails (EXDEV error), falling back to copy+delete which was not implemented in the worker
Orphaned shard files accumulated in /tmp until disk exhaustion; no cleanup mechanism existed for failed temp files

The fix and how to prevent it

Searchable error signature

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Migration workers report "No space left on device" errors

Use this text as a lookup key in logs and upstream issue trackers. It is not presented as a captured customer log. Confirm the cause from your own preceding events, versions, configuration and the cited references.

The fix and the prevention pattern

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