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Documentation Index

Fetch the complete documentation index at: https://www.thundercompute.com/docs/llms.txt

Use this file to discover all available pages before exploring further.

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What is Ephemeral Storage?

Ephemeral storage is fast, local disk space mounted at /ephemeral on your instance. It uses high-performance NVMe drives directly attached to the host machine, making it significantly faster than the persistent disk for I/O-heavy workloads.
Ephemeral storage is temporary. Data on /ephemeral is lost when you modify, delete, or migrate your instance. It is also not included in snapshots.

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When to Use Ephemeral Storage

Ephemeral storage is ideal for data that is large, frequently accessed, and easy to re-download:
  • Model weights downloaded from Hugging Face or other registries
  • Pip/conda caches to speed up environment rebuilds
  • Training checkpoints (back up important ones to persistent disk or cloud storage)
  • Large datasets that can be re-fetched
  • Scratch files from preprocessing or intermediate computation
For data you need to keep, use the persistent disk (your home directory) or snapshots.

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Configuring Ephemeral Storage

Ephemeral storage defaults to 0 GB (disabled). You can add it when creating or modifying an instance. 
# Create with ephemeral storage
tnr create --ephemeral-disk 200

# Add to an existing instance
tnr modify <instance_id> --ephemeral-disk 200

# Disable ephemeral storage
tnr modify <instance_id> --ephemeral-disk 0

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Size Limits

See thundercompute.com/pricing for current ephemeral storage limits by instance mode.

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Using Ephemeral Storage

Once configured, the storage is available at /ephemeral inside your instance: 
# Check available space
df -h /ephemeral

# Download model weights to ephemeral storage
huggingface-cli download meta-llama/Llama-3-8B --local-dir /ephemeral/llama-3-8b

# Use as pip cache
pip install --cache-dir /ephemeral/pip-cache transformers

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What Happens to Ephemeral Data

EventEphemeral dataPersistent disk
Instance runningPreservedPreserved
Modify instanceLostPreserved
Delete instanceLostLost
Create snapshotNot includedIncluded
Restore from snapshotEmptyRestored

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Best Practices

  1. Store only re-downloadable data on /ephemeral. Anything important should live on your persistent disk or be backed up to cloud storage.
  2. Use symlinks to redirect cache directories to ephemeral storage: 
    mkdir -p /ephemeral/huggingface
ln -s /ephemeral/huggingface ~/.cache/huggingface
  3. Set environment variables to point tools at ephemeral storage: 
    export HF_HOME=/ephemeral/huggingface
export PIP_CACHE_DIR=/ephemeral/pip-cache
export TRANSFORMERS_CACHE=/ephemeral/huggingface/transformers
  4. Back up training checkpoints periodically from /ephemeral to your home directory or cloud storage if you need to keep them.