# Storage Options

For comprehensive details about the storage systems available on Aire and Calder, please refer to the [Storage and Filesystem](page:storage-filesystem) section.

## Using Scratch on Lustre (disk-based)

Scratch on Lustre provides shared, high-capacity storage for large datasets and active project data. The path to this storage is set automatically in your job as the environment variable `$SCRATCH`.

::::{tab-set}

:::{tab-item} Aire

On Aire, `$SCRATCH` typically points to `/mnt/scratch/<username>` (symlinked as `/scratch`).

:::

:::{tab-item} Calder

On Calder, `$SCRATCH` points to `/scratch-calder/<username>`.

:::
::::

```{note}
When the upgraded Aire system (Aire 2.0) launches, Aire's scratch path is expected to be renamed to `/scratch-aire`; this page will be updated once that change is confirmed.
```

## Using Flash on Lustre (NVMe‑based)

Flash on Lustre provides high-performance, NVMe-based temporary storage, ideal for I/O‑intensive workloads and jobs requiring rapid access to large datasets across multiple nodes. The path to this storage is set automatically in your job as the environment variable `$TMP_SHARED`.

::::{tab-set}

:::{tab-item} Aire

On Aire, `$TMP_SHARED` typically points to `/mnt/flash/tmp/job.<JOB-ID>`.

:::

:::{tab-item} Calder

On Calder, `$TMP_SHARED` points to `/flash-calder/tmp/job.<JOB-ID>`.

:::
::::

```{note}
When the upgraded Aire system (Aire 2.0) launches, Aire's flash path is expected to be renamed to `/flash-aire`; this page will be updated once that change is confirmed.
```

To utilise Flash storage in your job, reference `$TMP_SHARED` in your submission script. For example:

```bash
#!/bin/bash
#SBATCH --job-name=example
#SBATCH --time=01:00:00

# Flash storage path is automatically set as $TMP_SHARED
echo "Flash storage path: $TMP_SHARED"

# Copy input data to Flash storage
cp -r /path/to/input/data $TMP_SHARED/

./example.bin --data $TMP_SHARED/data

# Copy results back to permanent storage
cp -r $TMP_SHARED/results /path/to/permanent/storage/
```

:::{note}
Data stored in Flash is automatically purged when the job finishes. Always copy important results back to permanent storage before your job ends.
:::

## Using Scratch on compute nodes

Scratch storage on compute nodes is accessed via the environment variables `$TMP_LOCAL` or `$TMPDIR`, which typically point to `/tmp/job.<JOB-ID>`. This storage is ideal for single-node jobs that require fast, localised access to temporary data.

To utilise it, reference `$TMP_LOCAL` or `$TMPDIR` in your submission script. For example:

```bash
#!/bin/bash
#SBATCH --job-name=example
#SBATCH --time=01:00:00

# Local scratch storage path is set as $TMP_LOCAL or $TMPDIR
echo "Local scratch path: $TMP_LOCAL"

# Copy input data to local scratch
cp -r /path/to/input/data $TMP_LOCAL/

./example.bin --data $TMP_LOCAL/data

# Copy results back to permanent storage
cp -r $TMP_LOCAL/results /path/to/permanent/storage/
```

:::{note}
Data stored in `$TMP_LOCAL` or `$TMPDIR` is automatically deleted when the job ends. Ensure you copy any important results back to permanent storage before your job completes.
:::