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

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

For the global /scratch, before submitting your job, copy your inputs into a folder on the /scratch (ie /scratch/login/whatever/). The simplest is to reproduce the same hierarchy of folders and files by changing /home by /scratch (copy with cp -r ).

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.