> ## 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.

# Ephemeral Storage

> Mount temporary data mounted at /ephemeral. Speed up training and installs with fast NVMe storage for weights, caches, and scratch data.

## 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.

<Warning>
  Ephemeral storage is temporary. Data on `/ephemeral` is lost when you modify, delete, or migrate your instance. It is also not included in snapshots.
</Warning>

## 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](/cli/operations/snapshots).

## Configuring Ephemeral Storage

Ephemeral storage defaults to **0 GB** (disabled). You can add it when creating or modifying an instance.

<Tabs>
  <Tab title="CLI">
    ```bash theme={null}
    # 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
    ```
  </Tab>

  <Tab title="VS Code">
    Set the **Ephemeral Storage** field in the create or modify instance dialog.
  </Tab>

  <Tab title="Console">
    Set the **Ephemeral Storage** field in the create or modify instance dialog.
  </Tab>
</Tabs>

### Size Limits

See [thundercompute.com/pricing](https://www.thundercompute.com/pricing) for current ephemeral storage limits by instance mode.

## Using Ephemeral Storage

Once configured, the storage is available at `/ephemeral` inside your instance:

```bash theme={null}
# 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
```

## What Happens to Ephemeral Data

| Event                 | Ephemeral data | Persistent disk |
| --------------------- | -------------- | --------------- |
| Instance running      | Preserved      | Preserved       |
| Modify instance       | Lost           | Preserved       |
| Delete instance       | Lost           | Lost            |
| Create snapshot       | Not included   | Included        |
| Restore from snapshot | Empty          | Restored        |

## 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:
   ```bash theme={null}
   mkdir -p /ephemeral/huggingface
   ln -s /ephemeral/huggingface ~/.cache/huggingface
   ```

3. **Set environment variables** to point tools at ephemeral storage:
   ```bash theme={null}
   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.