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Permanent Filesystems

Hint

Do not use permanent filesystems as work directories:

  • Even temporary files are kept in the snapshots and in the backup tapes over a long time, senselessly filling the disks,
  • By the sheer number and volume of work files, they may keep the backup from working efficiently.

Global /home Filesystem

Each user has 50 GiB in a /home directory independent of the granted capacity for the project. The home directory is mounted with read-write permissions on all nodes of the ZIH system.

Hints for the usage of the global home directory:

  • If you need distinct .bashrc files for each machine, you should create separate files for them, named .bashrc_<machine_name>

If a user exceeds her/his quota (total size OR total number of files) she/he cannot submit jobs into the batch system. Running jobs are not affected.

Note

We have no feasible way to get the contribution of a single user to a project's disk usage.

Global /projects Filesystem

For project data, we have a global project directory, that allows better collaboration between the members of an HPC project. Typically, all members of the project have read/write access to that directory. It can only be written to on the login and export nodes.

Note

On compute nodes, /projects is mounted as read-only, because it must not be used as work directory and heavy I/O.

Snapshots

A changed file can always be recovered as it was at the time of the snapshot. These snapshots are taken (subject to changes):

  • from Monday through Saturday between 06:00 and 18:00 every two hours and kept for one day (7 snapshots)
  • from Monday through Saturday at 23:30 and kept for two weeks (12 snapshots)
  • every Sunday st 23:45 and kept for 26 weeks.

To restore a previous version of a file:

  1. Go to the parent directory of the file you want to restore.
  2. Run cd .snapshot (this subdirectory exists in every directory on the /home filesystem although it is not visible with ls -a).
  3. List the snapshots with ls -l.
  4. Just cd into the directory of the point in time you wish to restore and copy the file you wish to restore to where you want it.

Note

The .snapshot directory is embedded in a different directory structure. An ls ../.. will not show the directory where you came from. Thus, for your cp, you should use an absolute path as destination.

Backup

Just for the eventuality of a major filesystem crash, we keep tape-based backups of our permanent filesystems for 180 days.

Quotas

The quotas of the permanent filesystem are meant to help users to keep only data that is necessary. Especially in HPC, it happens that millions of temporary files are created within hours. This is the main reason for performance degradation of the filesystem.

Note

If a quota is exceeded - project or home - (total size OR total number of files) job submission is forbidden. Running jobs are not affected.

The following commands can be used for monitoring:

  • showquota shows your projects' usage of the filesystem.
  • quota -s -f /home shows the user's usage of the filesystem.

In case a quota is above its limits:

  • Remove core dumps and temporary data
  • Talk with your colleagues to identify unused or unnecessarily stored data
  • Check your workflow and use /tmp or the scratch filesystems for temporary files
  • Systematically handle your important data: