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Merlin6 Storage	28 June 2019	merlin6_sidebar	/merlin6/data-directories.html	/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:

/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:

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:

  /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

/data/user/$username

Users can check their quota by running the following command:

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 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:

/data/project/$username

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

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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