---
title: Merlin6 Storage
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#keywords:
last_updated: 28 June 2019
#summary: ""
sidebar: merlin6_sidebar
redirect_from: /merlin6/data-directories.html
permalink: /merlin6/storage.html
---

## Merlin6 directory structure

Merlin6 offers the following directory classes for users:

* ``/psi/home/<username>``: Private user **home** directory
* ``/data/user/<username>``: Private user **data** directory
* ``/data/project/general/<projectname>``: Shared **Project** directory
   * For BIO experiments, a dedicated ``/data/project/bio/$projectname`` exists.
* ``/scratch``: Local *scratch* disk (only visible by the node running a job).
* ``/shared-scratch``: Shared *scratch* disk (visible from all nodes).

Properties of the directory classes:

| Directory                          | Block Quota [Soft:Hard] | Block Quota [Soft:Hard] | Quota Change Policy: Block        | Quota Change Policy: Files       | Backup |  Backup Policy                 |
| ---------------------------------- | ----------------------- | ----------------------- |:--------------------------------- |:-------------------------------- | ------ | :----------------------------- |
| /psi/home/$username                | USR [10GB:11GB]         | *Undef*                 | Up to x2 when strictly justified. | N/A                              | yes    | Daily snapshots for 1 week     |
| /data/user/$username               | USR [1TB:1.074TB]       | USR [1M:1.1M]           | Inmutable. Need a project.        | Changeable when justified.       | no     | Users responsible for backup   |
| /data/project/bio/$projectname     | GRP [1TB:1.074TB]       | GRP [1M:1.1M]           | Subject to project requirements.  | Subject to project requirements. | no     | Project responsible for backup |
| /data/project/general/$projectname | GRP [1TB:1.074TB]       | GRP [1M:1.1M]           | Subject to project requirements.  | Subject to project requirements. | no     | Project responsible for backup |
| /scratch                           | *Undef*                 | *Undef*                 | N/A                               | N/A                              | no     | N/A                            |
| /shared-scratch                    | *Undef*                 | *Undef*                 | N/A                               | N/A                              | no     | N/A                            |

### User home directory

This is the default directory users will land when login in to any Merlin6 machine.
It is intended for your scripts, documents, software development, and other files which
you want to have backuped. Do not use it for data or HPC I/O-hungry tasks.

This directory is mounted in the login and computing nodes under the path:

```bash
/psi/home/$username
```

Home directories are part of the PSI NFS Central Home storage provided by AIT and
are managed by the Merlin6 administrators.

Users can check their quota by running the following command:

```bash
quota -s
```

#### Home directory policy

* Read **[Important: Code of Conduct](## Important: Code of Conduct)** for more information about Merlin6 policies.
* Is **forbidden** to use the home directories for IO intensive tasks
   * Use ``/scratch``, ``/shared-scratch``, ``/data/user`` or ``/data/project`` for this purpose.
* Users can retrieve up to 1 week of their lost data thanks to the automatic **daily snapshots for 1 week**.
Snapshots can be accessed at this path:

   ```bash
   /psi/home/.snapshop/$username
   ```

### User data directory

The user data directory is intended for *fast IO access* and keeping large amounts of private data.
This directory is mounted in the login and computing nodes under the directory

 ```bash
/data/user/$username
```

Users can check their quota by running the following command:

```bash
mmlsquota -u <username> --block-size auto merlin-user
```

#### User data directory policy

* Read **[Important: Code of Conduct](## Important: Code of Conduct)** for more information about Merlin6 policies.
* Is **forbidden** to use the data directories as ``scratch`` area during a job runtime.
   * Use ``/scratch``, ``/shared-scratch`` for this purpose.
* No backup policy is applied for user data directories: users are responsible for backing up their data.

### Project data directory

This storage is intended for *fast IO access* and keeping large amounts of a project's data, where the data also can be
shared by all members of the project (the project's corresponding unix group). We recommend to keep most data in
project related storage spaces, since it allows users to coordinate. Also, project spaces have more flexible policies
regarding extending the available storage space.

You can request a project space by submitting an incident request via  **[PSI Service Now](https://psi.service-now.com/psisp)** using the subject line

   ```
   Subject: [Merlin6] Project Request for project name xxxxxx
   ```

Please list your wish for a project name and list the accounts that should be part of it. The project will receive a corresponding unix group.

The project data directory is mounted in the login and computing nodes under the dirctory:

```bash
/data/project/$username
```

Project quotas are defined on a per *group* basis. Users can check the project quota by running the following command:

```bash
mmlsquota -j $projectname --block-size auto -C merlin.psi.ch merlin-proj
```

#### Project Directory policy

* Read **[Important: Code of Conduct](## Important: Code of Conduct)** for more information about Merlin6 policies.
* It is **forbidden** to use the data directories as ``scratch`` area during a job's runtime, i.e. for high throughput I/O for a job's temporary files. Please Use ``/scratch``, ``/shared-scratch`` for this purpose.
* No backups: users are responsible for managing the backups of their data directories.

### Scratch directories

There are two different types of scratch storage: **local** (``/scratch``) and **shared** (``/shared-scratch``).

**local** scratch should be used for all jobs that do not require the scratch files to be accessible from multiple nodes, which is trivially
true for all jobs running on a single node.
**shared** scratch is intended for files that need to be accessible by multiple nodes, e.g. by a MPI-job where tasks are spread out over the cluster
and all tasks need to do I/O on the same temporary files.

**local** scratch in Merlin6 computing nodes provides a huge number of IOPS thanks to the NVMe technology. **Shared** scratch is implemented using a distributed parallel filesystem (GPFS) resulting in a higher latency, since it involves remote storage resources and more complex I/O coordination.

``/shared-scratch`` is only mounted in the *Merlin6* computing nodes (i.e. not on the login nodes), and its current size is 50TB. This can be increased in the future.

The properties of the available scratch storage spaces are given in the following table

| Cluster | Service        | Scratch      | Scratch Mountpoint | Shared Scratch | Shared Scratch Mountpoint | Comments                              |
| ------- | -------------- | ------------ | ------------------ | -------------- | ------------------------- | ------------------------------------- |
| merlin5 | computing node | 50GB  / SAS  | ``/scratch``       | ``N/A``        | ``N/A``                   | ``merlin-c-[01-64]``                  |
| merlin6 | login node     | 100GB / SAS  | ``/scratch``       | ``N/A``        | ``N/A``                   | ``merlin-l-0[1,2]``                   |
| merlin6 | computing node | 1.3TB / NVMe | ``/scratch``       | 50TB / GPFS    | ``/shared-scratch``       | ``merlin-c-[001-022,101-122,201-222`` |
| merlin6 | login node     | 2.0TB / NVMe | ``/scratch``       | ``N/A``        | ``N/A``                   | ``merlin-l-00[1,2]``                  |

#### Scratch directories policy

* Read **[Important: Code of Conduct](## Important: Code of Conduct)** for more information about Merlin6 policies.
* By default, *always* use **local** first and only use **shared** if your specific use case requires it.
* Temporary files *must be deleted at the end of the job by the user*.
   * Remaining files will be deleted by the system if detected.

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