Merge pull request #2 from boegel/rhel9

tweaks to page on migration to RHEL9 + rename to /rhel9

mkdocs/docs/HPC/index.md

@@ -20,6 +20,7 @@ Use the OS dropdown in the top bar to switch to a different operating system.
 - [Recording of HPC-UGent intro](https://www.ugent.be/hpc/en/training/introhpcugent-recording)
 - [Linux Tutorial](linux-tutorial/index.md)
 - [Hardware overview](https://www.ugent.be/hpc/en/infrastructure)
+- [Migration of cluster and login nodes to RHEL9 (starting Sept'24)](rhel9.md)
 {%- endif %}
 - [FAQ](FAQ.md) | [Troubleshooting](troubleshooting.md) | [Best practices](./best_practices.md) | [Known issues](known_issues.md)
 

mkdocs/docs/HPC/rhel9.md

@@ -0,0 +1,159 @@
+# Migration to RHEL 9 operation system (Tier-2)
+
+Starting September 2024 we will gradually migrate the HPC-UGent Tier-2 clusters that
+are using RHEL 8 as operating system (OS) to **RHEL 9 (Red Hat Enterprise Linux 9)**.
+This includes clusters `skitty`, `joltik`, `doduo`, `accelgor`, `donphan` and `gallade`
+(see also the [infrastructure overview](https://www.ugent.be/hpc/en/infrastructure)),
+as well as switching the Tier-2 login nodes to new ones running RHEL 9.
+
+## Motivation
+
+Migrating to RHEL 8 is done to bring all clusters in line with the most recent
+cluster that are already running RHEL 9 (`shinx`).
+
+This makes the maintenance of the HPC-UGent Tier-2 infrastructure significantly easier,
+since we only need to take into account a single operating system version going forward.
+
+It will also bring you the latest versions in operating system software, with more
+features, performance improvements, and enhanced security.
+
+## Impact on the HPC-UGent Tier-2 login nodes {: #login_nodes_impact }
+
+As a general rule, the OS of the login node should match the OS of the cluster
+you are running on. To make this more transparent, you will be warned when loading
+a `cluster` module for a cluster than is running an OS that is different than that
+of the login node you are on.
+
+For example, on the current login nodes (`gligar07` + `gligar08`) which are still using RHEL 8,
+you will see a warning like:
+```
+$ module swap cluster/shinx
+...
+We advise you to log in to a RHEL 9 login node when using the shinx cluster.
+The shinx cluster is using RHEL 9 as operating system,
+while the login node you are logged in to is using RHEL 8.
+To avoid problems with testing installed software or submitting jobs,
+it is recommended to switch to a RHEL 9 login node by running 'ssh login9'.
+```
+
+Initially there will be only one RHEL 9 login node. As needed a second one will be added.
+
+When the default cluster (`doduo`) is migrated to RHEL 9 the corresponding login nodes
+will also become default when you log in via `login.hpc.ugent.be`
+When they are no longer needed the RHEL 8 login nodes will be shut down.
+
+### User limits (CPU time, memory, ...) {: #login_nodes_limits }
+
+To encourage only using the login nodes as an entry point to the HPC-UGent infrastructure,
+user limits will be enforced on the RHEL 9 login nodes. This was already the case for the
+RHEL 8 login nodes, but the limits are a bit stricter now.
+
+This includes (per user):
+
+* max. of 2 CPU cores in use
+* max. 8 GB of memory in use
+
+For more intensive tasks you can use the
+[interactive and debug clusters](interactive_debug.md)
+through the [web portal](web_portal.md).
+
+## Impact on central software stack {: #software_impact }
+
+The migration to RHEL 8 as operating system should not impact your workflow,
+everything will basically be working as it did before (incl. job submission, etc.).
+
+However, there will be impact on the availability of software that is made available via modules.
+
+**Software that was installed with an older compiler toolchain will no
+longer be available once the clusters have been updated to RHEL 9.**
+
+This includes all software installations on top of a compiler toolchain that is older than:
+
+* `GCC(core)/12.3.0`
+* `foss/2023a`
+* `intel/2023a`
+* `gompi/2023a`
+* `iimpi/2023a`
+* `gfbf/2023a`
+
+(or another toolchain with a year-based version older than `2023a`)
+
+The `module` command will produce a clear warning when you are loading modules
+that are using a toolchain that will no longer be available after the cluster
+has been migrated to RHEL 9.
+For example:
+
+```
+foss/2022b:
+   ___________________________________
+  /  This module will soon no longer  \
+  \  be available on this cluster!    /
+   -----------------------------------
+         \   ^__^
+          \  (xx)\_______
+             (__)\       )\/\
+              U  ||----w |
+                 ||     ||
+
+Only modules installed with a recent toolchain will still be available
+when this cluster has been migrated to the RHEL 9 operating system.
+Recent toolchains include GCC(core)/12.3.0, gompi/2023a, foss/2023a,
+iimpi/2023a, intel/2023a, gfbf/2023a, and newer versions.
+
+You should update your workflow or job script to use more recent software
+installations, or accept that the modules you currently rely on will soon
+no longer be available.
+
+To request a more recent version of the software you are using,
+please submit a software installation request via:
+
+https://www.ugent.be/hpc/en/support/software-installation-request
+
+The HPC-UGent Tier-2 clusters running RHEL 8 will be migrated to RHEL 9.
+
+For more information, see https://docs.hpc.ugent.be/rhel9/
+
+If you have any questions, please contact hpc@ugent.be .
+```
+
+If you require software that is currently only available with an older toolchain
+on the HPC-UGent Tier-2 clusters that are still running RHEL 8,
+check via `module avail` if a more recent version is installed that you can switch to,
+or submit a [software installation request](https://www.ugent.be/hpc/en/support/software-installation-request)
+so we can provide a more recent installation of that software which you can adopt.
+
+It is a good idea to test your software on the `shinx` cluster,
+which is already running RHEL 9 as operating system,
+to be sure if it still works.
+We will provide more RHEL 9 nodes on other clusters to test on soon.
+
+## Planning
+
+We plan to migrate the HPC-UGent Tier-2 clusters that are still
+using RHEL 8 to RHEL 9 one by one, following the schedule outlined below.
+
+| ***cluster*** | ***migration start*** | ***migration completed on*** |
+| --- | ---- | --- |
+| `skitty` | Monday 30 September 2024 | |
+| `joltik` | October 2024 | |
+| `accelgor` | November 2024 | |
+| `gallade` | December 2024 | |
+| `donphan` | February 2025 | |
+| `doduo` (default cluster) | February 2025 | |
+| login nodes switch | February 2025 | |
+
+Migration the `donphan` and `doduo` clusters to RHEL 9 and switching `login.hpc.ugent.be` to RHEL 9 login nodes
+will be done at the same time.
+
+We will keep this page up to date when more specific dates have been planned.
+
+!!! warning
+    This planning below is subject to change, some clusters may get migrated
+    later than originally planned.
+
+    Please check back regularly.
+
+## Questions
+
+If you have any questions related to the migration to the RHEL 9 operating system,
+please [contact the {{ hpcteam }}]({{ hpc_support_url }}).