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The Alps System

Alps is a distributed high-performance computing (HPC) infrastructure managed by CSCS. Unlike traditional HPC systems, it is composed of several logical units called vClusters (versatile clusters).

From a user's perspective, these vClusters play the role of traditional HPC machines, with each one tailored to the needs of a specific community.

This setup also enables geographical distribution of vClusters which facilitates geo-redundancy. The main physical component of Alps is hosted at CSCS in Lugano and a detailed description can be found in their documenation .

vClusters

The following table shows current clusters distribution on Alps at CSCS (only C2SM relevant clusters are shown).

vCluster Activity Share C2SM Support
Santis Weather & Climate ~ 430 Grace-Hopper nodes ✅
Balfrin MeteoSwiss ~ 40 A100 GPU nodes ✅
Eiger CPU-only workloads ~ 580 multicore nodes 🟡
Daint User Lab ~ 600 Grace-Hopper nodes ❌
Clariden Machine Learning ~ 800 Grace-Hopper nodes ❌

✅ Full C2SM support
🟡 Partial or limited C2SM support (help available on request)
❌ No C2SM support

More information about clusters on Alps is available on the official CSCS documentation .

Access

Connection to vClusters happens as for any other CSCS machine, e.g. ssh santis.cscs.ch with a ProxyJump on ela.cscs.ch. A section in the ~/.ssh/config could look as follows:

~/.ssh.config
Host ela
  Hostname ela.cscs.ch
  User cscsusername
  IdentityFile ~/.ssh/cscs-key

Host santis* daint* 
  Hostname %h.alps.cscs.ch
  User cscsusername
  IdentityFile ~/.ssh/cscs-key
  ProxyJump ela

Host balfrin* 
  Hostname %h.cscs.ch
  User cscsusername
  IdentityFile ~/.ssh/cscs-key
  ProxyJump ela

This allows standard connections like ssh santis, but you can also specify a login node if needed, e.g., ssh santis-ln002. Replace cscsusername with your actual username.

User Environments

Software stacks at CSCS are now accessible through the so-called User Environments (uenv). User environments contain the minimal software stack required for a certain activity, say, building and running ICON. They are generated by spack, packed into single squashfs file and then mounted by the user. In a way, they can be considered as poor man's containers.

Main Advantages of Uenvs

To a large degree, we can consider that there is a separation of concerns between software stacks and the machine OS which enables the following:

  • a much reduced maintenance of software stacks
  • system-wide upgrades are limited to the low level OS, so should be way easier, when not transparent to the users
  • upgrading to more recent software stacks or keeping old ones around (think compiler versions) is way easier
  • users (for now C2SM) are able to build their own uenvs
  • quicker access to software compared to classical multi-files directories

CSCS Documentation

A description of user environments and the uenv tool can be found in the CSCS documentation .

Support by CSCS

General information about access, file systems, vClusters, user environments and much more can be found at the CSCS documentation .

To contact CSCS staff directly, users can join their dedicated Slack workspace , with dedicated channels for each vCluster.

Introductory Workshop Material

As an introduction to the Alps infrastructure, the material of our C2SM workshop "Switching to Alps" from August 12, 2024 is available: