There are a number of file systems on DIaL2.5 that should be used in different ways:

• /home
• /scratch
• /data
• /tmp

/home

Every user has a home directory within the /home file system. This will be your current working directory on ALICE. The home directory path is derived from your user name, e.g. user xyz2 would have a home directory located at /home/xyz2.

The home directory should only be used to store program code, job submission scripts, configuration files and small amounts of data.

Your home directory can be referenced on the Linux command line with the shorthand ~. The simple command cd with no arguments will return you to your home directory.

Users' home directories are backed up nightly.

/scratch

You will have a scratch directory on the scratch file system for each project that you are associated with.

The location will be /scratch/project/username - so users in multiple projects will have several to choose from. As each user's scratch directory is readable by other members of the same project, it's important to choose the correct one depending on which project is being worked on.

The directory /scratch/project/shared has special permissions to ensure that all files within are always owned by the project group.

The scratch directory used should be the main location for job files, and generally should be used as the working directory for jobs. The scratch space has quotas applied which are in line with those requested for “work” in DiRAC time applications. These are not allocations, only quotas, so can add up to more than the available storage.

Files within /scratch are not backed up. Furthermore, there is an automated process which deletes any files that haven't been accessed in more than 60 days. There will be no prior warning that files will be deleted, it is up to users to ensure that important data is not kept in /scratch for long term storage.

/data

This file system is provided for medium term storage of results prior to publication and transfer of data to the users own institution. The structure of the filesystem is similar to /scratch. It is also not backed up and will be swept of old data. The data sweeping will be based on modification times being more than 9 months.

/tmp

Each compute node has a small amount of local disc mounted on /tmp. For some jobs there may be a performance gain over /tmp in using this file system for intermediate files.

Standard compute nodes have 100GB available. The preferred way to use /tmp within a job is to refer to it using the environment variable $TMPDIR. This way the job's files are cleaned-up when the job finishes automatically. Otherwise it is your job's responsibility to remove files from the local file system when it ends.

The /tmp file system is not backed up, and the contents are deleted whenever the compute node reboots for any reason.

Files on /tmp should only be considered safe for the duration of the job which they belong to.