The /scratch is a temporary workspace that you can use to copy your input data and write your calculation outputs. The pros of working in the /scratch are the following:

• offers a bigger volume than the volume available in your /home space (many /scratch workspaces are available),
• increase processing speed of reads/writes,
• increase the simultaneous I/O.

Scratches are shared and common storages, their performances depends on your proper use. Hence, they must not contain:

• documentation (lots of useless small files) ⇒ /home,
• symbolic links (tiny files),
• programs or exe (useless I/O) ⇒ /home.

Two types of /scratch are available:

As we have various clusters of different generations of processors (Lake, the newest, E5 and X5, the former), we have several global scratches.

The /scratch/Lake/, common to CLG* and SLG* queues is available for all cluster Lake nodes.

It contains /scratch/Lake/lake-gfs-scratch, as a empty check file.

It is accessible from cluster Lake front machines

/scratch/
     ├── Lake/         (common to Lake cluster)
     ├── disk/         (local to some servers)
     ├── Chimie/       (reserved to chimie usage)
     ├── Bio/          (reserved to biologie usage)
     ...
     └── Project_name/ (reserved to some servers, 
                        with dedicated hardware)

The /scratch/E5N/, common to E5-* queues is available for all cluster E5 nodes.

It contains /scratch/E5N/E5N-gfs-scratch, as a empty check file.

It is accessible from cluster E5 front machines

/scratch/
     ├── E5N/          (E5 scratch, common to E5 cluster)
     ├── nvme/         (local to some servers)
     ├── ssd/          (local to some servers)
     ...
     └── Project_name/ (local to some servers, 
                        with dedicated hardware)

The /scratch/X5/, common to X5-* queues is available for all cluster x55/x56 nodes.

It contains /scratch/X5/x5570-gfs-scratch, as a empty check file.

It is accessible from cluster x55/x56 front machines

/scratch/
     └── X5/           (X5 scratch, common to X5 cluster)

Some local /scratch are available only on some nodes. See detailled description or ask staff.

The diagram below represents the integration of these /scratch spaces in the PSMN infrastructure.

These locals /scratch are only avaiable in some nodes of the cluster see more complete description .

For global /scratch, before submitting your job, copy your inputs into a folder on the /scratch/ (ie /scratch/<cluster>/<login>/whatever/).

The simplest is to reproduce the same hierarchy of folders and files by changing /home by /scratch/<cluster>.

Do not forget to modify your submitting files consequently.

At the end of the run, retrieve your results manually, in the / scratch, from any of the corresponding front nodes.

For local /scratch you don't know which node will be assigned to your job (it is also valid for the global scratch, but less annoying). Thus, You cannot copy your data to a particular node in advance. You must integrate the copy /scratch ↔ /home in the submitted script.

Examples are available here.

We don't have a sample script that cleans up automatically. Similarly, if you don't feel comfortable with these scripts, do not hesitate to come and talk about during a Tuesday coffee session.