Login nodes
===========

.. IMPORTANT:: **Login nodes are not for computing**

    Login nodes are shared among many users and therefore must **not** be used to run computationally intensive tasks. Those should be submitted to the scheduler which will dispatch them on compute nodes.


.. NOTE:: **Do and Don'ts**

    * Avoid running calculations (with large :term:`IOPS`) on the home disk,
    * Always use the queueing system,
    * Login nodes are for editing files, transfering files and submitting jobs,
    * Login nodes should be used to build specific binaries,
    * Do not run calculations interactively on the login nodes,
    * Offenders process will be killed **without warnings**!


The key principle of a shared computing environment is that resources are shared among users and must be scheduled. It is mandatory to schedule work by submitting jobs to the scheduler on PSMN's clusters. **And since login nodes are shared resources, they must not be used to execute computing tasks**.

Acceptable use of login nodes include:

* file transfers and file manipulations (compression, decompression, etc),
* script and configuration file editing,
* binary building, compilation,
* short binary tests with small input/output (~10mn CPU time),
* lightweight workflow tests on small datasets (~10mn CPU time),
* job submission and monitoring.

.. TIP:: **You can submit jobs from any login node to any partition. Login nodes are only segregated for build (CPU microarchitecture) and scratch access.**

Here is a list of login nodes :

+------------+---------------------+------------------+
| Partition  |  login/build nodes  | IB scratch       |
+============+=====================+==================+
|  **None**  |  x5570comp[1-2]     | **None**         |
+------------+---------------------+------------------+
|  E5        | e5-2667v4comp[1-2], | /scratch/E5N     |
|            |          c8220node1 |                  |
+------------+---------------------+------------------+
| E5-GPU     | r730gpu01           | /scratch/Lake    |
+------------+---------------------+------------------+
|  Lake      | m6142comp[1-2],     | /scratch/Lake    |
|            | cl5218comp[1-2],    |                  |
|            | cl6242comp[1-2],    |                  |
|            | cl6226comp[1-2]     |                  |
+------------+---------------------+------------------+
|  Epyc      | **None**            | /scratch/Lake    |
+------------+---------------------+------------------+
|  Cascade   | s92node01           | /scratch/Cascade |
+------------+---------------------+------------------+

For example, to access ``/scratch/E5N/``, you have to login with either one of ``e5-2667v4comp1``, ``e5-2667v4comp2`` or ``c8220node1``.


Login nodes without partition
-----------------------------

+--------------------+---------------------+-------+---------+-------------+------------+--------+----------------+
| login nodes        | CPU Model           | cores | RAM     | ratio       | infiniband | GPU    | local scratch  |
+====================+=====================+=======+=========+=============+============+========+================+
| x5570comp[1-2]     | X5570 @ 2.93GHz     | 8     | 24 GiB  | 3 GiB/core  | N/A        | N/A    | N/A            |
+--------------------+---------------------+-------+---------+-------------+------------+--------+----------------+

These login nodes are the oldest. They are not connected to any partition (or cluster). **Usable for anything BUT builds** (jobs surveillance, files operations [edition, compression/decompression, copy/move, etc.], short testings, etc.). See also :doc:`partitions_overview`.

Binaries build on these, **with system defaults** (no loaded modules), *should* run on all partitions. Minimal GCC tuning: ``-mtune=generic -O2 -msse4a``.

.. TIP:: **You can submit jobs from any login node to any partition. Login nodes are only segregated for build (CPU microarchitecture) and scratch access.**


Visualization nodes
-------------------

See :doc:`../connection/visualization_server` for connection manual.

+---------------+-----------------+------------+---------+------------------+------------------+
| Host          | CPU family      | RAM        | Network | main Scratch     | GPU              |
+===============+=================+============+=========+==================+==================+
| r740visu      | Lake (8 cores)  | 192Gib     | 56Gb/s  |  /scratch/E5N    | Quadro P4000 8Gb |
+---------------+-----------------+------------+---------+------------------+------------------+
| r740gpu0[6-9] | Lake (16 cores) | 192/384Gib | 56Gb/s  |  /scratch/Lake   | T1000 8Gb        |
+---------------+-----------------+------------+---------+------------------+------------------+

* Nodes ``r740gpu0[6-9]`` have a local scratch on ``/scratch/local/`` (120 days lifetime residency),
* Some visualization servers are not listed here, due to restricted access. Contact PSMN's Staff or your PSMN's group correspondent for more.