Blogpost eessi musica

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+        ignore_words_list: Fram,fram,ND,nd,Linz
 
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docs/blog/.authors.yml

@@ -119,3 +119,8 @@ authors:
     description: European Molecular Biology Laboratory, Germany
     avatar: https://avatars.githubusercontent.com/u/44709261?v=4
     slug: https://github.com/stefanomarangoni495
+  admccartney:
+    name: Adam McCartney
+    description: Austrian Scientific Computing (ASC), TU Wien
+    avatar: https://avatars.githubusercontent.com/u/35410331?v=4
+    slug: https://github.com/adammccartney

docs/blog/posts/2026/03/eessi-musica.md

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+---
+authors: [admccartney]
+date: 2026-03-27
+slug: eessi-musica
+---
+
+# Choosing EESSI as a base for MUSICA
+
+<figure markdown="span">
+    ![MUSICA](MUSICA-v2-32-Matthias_Heisler.jpg){width=75%}
+    <figcaption>(c) Matthias Heisler 2026</figcaption>
+</figure>
+
+MUSICA (Multi-Site Computer Austria) is the latest addition to Austria's
+national supercomputing infrastructure. The system's compute resources
+are distributed across three locations in Austria: Vienna, Innsbruck,
+and Linz. We describe the process that led to the adoption of EESSI
+as a base for the software stack on the MUSICA system at the Austrian
+Scientific Computing (ASC) research center.
+
+<!-- more -->
+
+The background section aims to provide a brief history of how cluster
+computing at ASC has evolved, with a particular focus on the various
+incarnations of the software stack. We outline our motivations for
+redesigning a system that delivers the software stack, for initial
+use on the MUSICA HPC system. We describe the timeline of events that
+lead to the experiments with EESSI and EasyBuild, and offer details of
+the two complementary approaches of building a software stack that we
+compared. Finally, we offer a critical reflection on our experiments
+and outline our ultimate reason for choosing to use EESSI as a base and
+blueprint for the software stack.
+
+
+## Background
+
+The ASC (formerly VSC) is a national center for high performance
+computing and research powered by scientific software. The flagship
+cluster VSC-1 was in service from 2009-2015, succeeded by a series of
+clusters (2-5)[^1]. VSC 4 and 5 are the two clusters that remain in
+service as of 2026, they will be joined in April 2026 by a new cluster
+MUSICA, which stands for Multi-Site Compute Austria. MUSICA is a GPU
+centric cluster run on OpenStack and has so far been the main testing
+ground for our initial experiments with EasyBuild and EESSI.
+
+The management of the software stack at ASC evolved along the following
+lines:
+
++ VSC 1, 2: Initially catered to small groups of expert users, all
+  software was installed manually 
+
++ VSC 3, 4: Still partially managed by hand. A set of scripting tools for
+  structuring software directory trees. These tools were initially copied
+  from Innsbruck and adapted to work on the VSC. Use of Tcl modules was also
+  adopted at this time.
+
++ VSC 4, 5: Spack introduced (reduced the need for custom install
+  scripts, install lots of software quickly, pull in dependencies
+  automatically)
+
+## Motivation
+
+Internal discussions led to a comprehensive understanding of where
+the current software stack was lacking and where it would ideally be.
+During the discussions, members of the user support team were able
+to clearly articulate the various use cases generated by users. This
+lead to setting a number of high level goals that were used to derive
+requirements. At a very high level, some of the more important goals can
+be summarized as:
+
+  - Improved reproducibility and redeployment.
+  - Establishment of clear release cycles.
+  - Creation of a more organized and user-friendly representations for the
+    cluster users.
+
+We articulated what an ideal software stack should look like, and we
+identified a number of issues with the way the software stack was
+currently managed.
+
+### Tooling & Presentation
+
+The way that we had been using Spack and Tcl Modules had lead to a
+fairly unmanageable situation on our clusters. To meet user requests
+for software, we adopted a pragmatic approach. This lead to a situation
+in which a myriad of software variants were installed into the shared
+file system hosting the systems' software. This quickly lead to a
+fairly overwhelming presentation of available modules to the user.
+Another major issue here was that there were significant issues around
+de duplication. We don't know the root cause of this, it may just have
+been a misconfigured Spack. In any case, we ended up in an untenable
+situation where certain dependencies would get installed many times
+over. For example, there were multiple installs of the same OpenMPI
+version on the system, all built slightly differently and most untested
+on the systems. This meant that there was no way to indicate to the user
+which version of a particular software was the one that worked.
+
+### Build procedure hard to reproduce
+
+During the last operating system upgrade, the need for a more automated
+build process was painfully felt. Because most software was built ad-hoc
+in response to user request, sometimes the only record of the build procedure
+were the build artefacts themselves. This meant manually going over a very large
+software repository and rebuilding everything more or less by hand for the new
+operating system.
+
+### Poor bus factor
+
+This one refers to the well known metric from software engineering about
+the degree of shared knowledge on a specialized domain within the team.
+How many people would have to be hit by a bus before the team could
+cease to carry out its work? In this particular case, the knowledge about the
+software stack was concentrated in one or two individuals.
+
+## Searching
+
+As outlined above, the numerous issues with the current stack
+established the frame in which to search for a set of tools and methods
+to ease the realisation of the high level goals for the software
+stack. To reiterate, manageability and user-friendliness were top of the list.
+
+
+### Timeline
+
+We formed the The Software And Modules (SAM) working group in Q4 2024.
+SAM consists of 5 people that are dedicating the majority of their
+time to exploring possible alternative ways of building, managing and
+presenting the software stack to users. The members draw on expertise
+from different areas, notably from their work on the user-support,
+sysadmin and platform teams. The goal for the new software stack was to
+have it up and running on the new MUSICA system towards the end of 2025.
+
++ *Summer 2024*:
+  Initial meetings that highlighted the need to reform the management
+  of software so that it could be easy to use, transparent and logical,
+  as well as tested and performant. This is the first mention of
+  EESSI/EasyBuild as possible alternatives to Spack and Lmod as an alternative
+  to Tcl Modules.
+
++ *Autumn 2024*:
+  Working group established and a broad set of tools and approaches were
+  compared, namely:
+    + an installation of Spack with Environment modules
+    + an installation of Guix
+    + an installation of EESSI
+  These tools were evaluated against a set of high level user
+  requirements that we agreed. The outcome was to focus on Easybuild and
+  EESSI.
+
++ *Winter 2024 - Spring 2025*:
+  Made the strategic decision to have EESSI installed on the MUSICA
+  system. Decided to run a small experiment whereby a small software
+  stack would be built and installed, in order to compare and contrast
+  approaches - "EESSI on the side" vs. "EESSI as a base"
+
++ *Summer 2025*:
+  In June 2025, the system entered a closed test phase. In this phase
+  the system was open to a small number of power users. The core
+  software provided by EESSI. The custom stack is extended during this
+  phase, in response to user software requests that center mostly around
+  proprietary software.
+
++ *Autumn 2025 - Winter 2025/2026*:
+  In November 2025 the MUSICA open test phase began. At this stage
+  anyone with an existing account at ASC was granted access to the
+  system upon request. At the end of the open test phase, users
+  participated in a survey. Generally the response was quite positive
+  towards the setup of the system.
+
+  - Users categorized their usage according to scientific domain, the largest
+    groups were:
+    Physics (45), AI (41), Chemistry (24), Data Science (15), Bioinformatics (11)
+
+  - In response to a question as to whether the module system was used, or if
+    the user relied on individual installations: 32 used the module system; 24
+    preferred an individual installation; 43 used a mixture of both.
+
+  - What did users used to build, install or run their software? Of 99
+    respondents:
+    + 63 Conda/Pip
+    + 21 EESSI-extend
+    + 16 None of these
+    + 15 Containers
+    + 13 buildenv
+    +  5 Spack
+
+  - 5/77 comments on the experience of compiling software on the
+    system explicitly mention using `LD_LIBRARY_PATH`. Despite having
+    highlighting the recommendation to use the `buildenv` modules when
+    compiling, the users preferred their own approach.
+    Generally the `buildenv` modules and usage of rpath wrappers is not
+    that well understood on the SAM team, so it's hard to explain to
+    users *why* the should be using this approach.
+
+
+## Experiments
+
+### Test stack
+
+The following programs were agreed upon as a way to come in to contact
+with specific workflows, such as writing easyconfig files, writing
+custom easybuild hooks, installing commercial software, installing gpu
+specific application software.
+
++ AOCC 5.0.0
++ Intel Compilers
++ Vasp 6.5.0
++ 1 Commercial software (starccm, mathematica)
++ NVHPC
++ VASP 6.5.0 GPU
++ Containers (singularity, docker, nvidia)
+
+### EESSI on the side
+
+This approach in a sense represents the traditional way to build a
+software stack, building everything directly on the host (Rocky9), and
+relying on system libraries. It used scripts and wrappers from the sse2
+toolkit from National Supercomputer Centre at Linköping University as
+a way to manage and structure the modules and software installations.
+The software builds were a mixture of EasyBuild scripts and makefiles.
+EESSI was offered as a module in its pure form and in general users were
+discouraged from using EESSI-extend, or at their own risk.
+
+### EESSI as a base
+
+With this approach, we leveraged EESSI-extend extensively and aimed to
+build the whole stack with the compatibility layer from EESSI as a base.
+The learning curve for building software more or less moved back and
+forth between three distinct phases, leveraging the various possible
+settings for the EESSI-extend module.
+
++ Phase 0 -> EESSI_USER_INSTALL
++ Phase 1 -> EESSI_SITE_INSTALL
++ Phase 2 -> EESSI_PROJECT_INSTALL=/cvmfs/software.asc.ac.at
+
+
+## Reflections
+
+### EESSI on the side
+
+By comparison, it was much quicker and easier to build all the software
+in list using this approach. It also offers a lot of control to the
+sysadmin who builds the software and doing things like tweaking or
+modifying module files in place was possible. The downsides were
+reproducibility and portability, there would be obvious work involved
+with building the stack again upon the next OS upgrade. That said,
+everything worked much more smoothly than with EESSI-extend, it was
+possible to build all the software that was listed and run basic tests
+with Slurm. We had some open questions around interoperability between
+custom modules and EESSI, and whether it would be problematic to mix
+modules from the two independent stacks without running into issues
+(probably not due to different libc versions).
+
+
+### EESSI as a base
+
+By the end of the closed test phase of MUSICA, the engineering team
+chose EESSI as the foundation for the software stack. While this approach
+introduced complexity into our build and installation workflows, it
+enabled us to meet certain key requirements for the MUSICA software
+infrastructure.
+
+Specifically, we leveraged CVMFS to distribute the software stack across
+the three sites - Vienna, Linz, and Innsbruck. EESSI offers access
+to approximately 1960 modules that are ready to load on the target
+architecture. Setting up EESSI was quite straight forward, and despite
+team members finding the many options of installing with EESSI-extend
+module too complex, adopting this method aligned with modern practices
+for managing HPC software. EESSI is open source, well documented, and
+maintained by colleagues within Europe's HPC ecosystem.
+
+Engaging with EESSI's documentation, source code, and community proved
+valuable. We identified a reusable blueprint that we could adapt to fit
+our specific needs. Despite the initial learning curve, this approach
+provided long-term benefits in terms of maintainability and scalability.
+
+
+---
+
+[^1]: <https://docs.vsc.ac.at/systems/>