start:fs_dm:filesystems:overview

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# File Systems on MOGON I and II

Essentially IBM's GPFS (re-branded to "Spectrum Scale") is MOGON I's file system, while MOGON II uses Lustre file system. Both are parallel file systems, meaning that the data is accessible on every client (indicated by the small boxes in the figure).

This distinction however is not absolute: The GPFS contents of the MOGON I project directories are exposed to Mogon II by means of NFS (Network File System), which is true for the home directory in particular.

Note that the other direction (exposing MOGON II's content to MOGON I) is intended, but not realized, yet.

Also note, that the different file systems and networks carry different properties, resulting in yet different best practices. These are outlined in the file system entries in this wiki.

In either case: Our filesystems are not a wastebasket for your data. The ZDV offers an archiving system – it is your responsibility to occasionally clean up or archive data.

The HOME directory on MOGON I for each user is a link to /gpfs/fs1/home/<username> visible as /home/<username>. On MOGON II this is the same directory, exposed by NFS.

Whilst the project directories (resp. their underlying file systems) are optimized for I/O of many big files, the home directory obviously cannot match this property: Small scripts, configuration files, aggregated results, etc. – this is what a home directory is for. Put negatively, this requires two restrictions or policies: The home directory is not for heavy I/O1), particularly not on MOGON II, as it is exposed via NFS to this cluster.

Looking on it the other way around, scripts, code, config files, small text files may go here, without second thoughts.

Currently the home directories have the following default setting:
• One million files per user
• a quota of 300 GiB.

The project directory on MOGON II currently resides under /lustre/miifs01/project/<projectname>. An analogous link to /m2_project/<projectname> as on MOGON I is intended, but not yet realized.

The purpose of this filesystem (and the related mountpoint) obviously is to place all data relevant to the project, which is not volatile (in contrast to the scratch filesystem, see below).

See our quota page for further information.

The scratch filesystem on MOGON II currently resides under /lustre/miifs03/scratch/<projectname>.

The purpose of this filesystem (and the related mountpoint) obviously is to place all data relevant to the project, which is volatile (in contrast to the project filesystem, see above).

Currently, there is no quota. Data can be deleted at any time, yet:

The only current policy is:

• When the file system usage crosses a certain threshold (70 % full), files will be deleted automatically.
• The deletion will start with the oldest files.

1)
We regret that we had to limit the home directory to a million files to prevent abuses.
2)
block size is 4 MB, meaning: each file smaller than 4 MB, will occupy 4 MB
• start/fs_dm/filesystems/overview.txt