Overview

Roihu and LUMI are CSC's supercomputers. Roihu, CSC's national supercomputer, has been available for CSC users since June 2026, replacing the retired Puhti and Mahti systems. LUMI is one of the pan-European pre-exascale supercomputers, located in CSC's data center in Kajaani. The CPU partition of LUMI (LUMI-C) has been available since early 2022, and the full system with the large LUMI-G partition has been available since early 2023.

Roihu consists of two main partitions: Roihu-CPU and Roihu-GPU that have separate login nodes and software environments. Roihu-CPU contains AMD EPYC CPUs and is intended for CPU-based computing, while Roihu-GPU provides GPU-accelerated computing with NVIDIA GH200 Grace Hopper Superchips. Roihu also supports jobs requiring larger amounts of memory than CSC's previous national supercomputers, and will provide enhanced support for sensitive data workloads.

CSC supercomputers use the Linux operating system and we recommend that you are familiar with basics of Linux command line usage before starting.

Note

For an overview of the LUMI supercomputer, see the LUMI documentation.

Accessing CSC supercomputers

To be able to use CSC's supercomputers, you need to have a CSC user account that belongs to a computing project which has access to the respective supercomputers. CSC user accounts and projects are managed in the MyCSC portal. Further instructions are provided in the Accounts section of this user guide.

Note

To access the LUMI supercomputer, you need to create a LUMI-specific project. For more details on getting started with LUMI, see the LUMI documentation.

Connecting to the supercomputers

SSH certificates are required to connect to Roihu over SSH

To connect to Roihu, users must sign their public key in MyCSC to obtain a time-based SSH certificate. Each certificate is valid for 24 hours, and once it expires, a new one must be generated by signing the public key again.

Read the detailed instructions on signing your public key.

Connect using an SSH client. Roihu has separate login nodes for the Roihu-CPU and Roihu-GPU partitions:

ssh username@roihu-cpu.csc.fi
# or
ssh username@roihu-gpu.csc.fi

These commands will connect you to one of the login nodes. If you need to connect to a specific login node, use the commands:

ssh username@roihu-cpu-login[1-4].csc.fi
# or
ssh username@roihu-gpu-login[1-2].csc.fi

Where username is the username you get from CSC.

For more details, see the connecting page.

Roihu can also be accessed via its web interface at www.roihu.csc.fi.

Scalability

Don't allocate more resources to your job than it can use efficiently. This needs to be verified for each new code and job type (different input) by a scaling test. The policy is that the job should be at least 1.5 times faster when you double the resources (cores). Instructions for performing a scalability test. Please also consider other important factors related to performance.

Projects and quotas

Working in CSC supercomputers is based on projects. The computing and storage resources are allocated to projects and when you start a batch job, you must always define the project that the job belongs to.

Projects are managed in the MyCSC portal, where you can add services, resources and users to your CSC projects.

In CSC supercomputers, you can check your currently active projects with the command:

csc-projects

This command shows information for all your CSC projects. You can select just one project to be reported with the -p option. For example:

[kkayttaj@roihu-cpu-login1 ~]$ csc-projects -p project_2012345
-----------------------------------------------------------------
Project: project_2012345        Owner: Kalle Käyttäjä
Title: "Ortotopology modeling"
Start: 2019-08-20 End: 2029-10-23 Status: open
Billing units      Budget        Used      Remain
-------------      ------        ----      ------
CPU BU:             60000          20       59980
GPU BU:              1000          30         970
Storage BU:        300000          40      299960
Cloud BU:             400          10         390
Latest resource grant: 2025-01-31
-----------------------------------------------------------------
Project info updated: 2025-09-02 15:12

The command reports the owner of the project, title, start and end dates. In addition the command prints out the budgeting information for the project: how many Billing Units of each type have been granted to your project, how many have been used and how many still remain.

The disk areas of your projects can be checked with the command:

csc-workspaces

Using CSC supercomputers

Systems: What computational resources are available
Usage policy: Usage policy of CSC supercomputers
Connecting: How to connect to CSC supercomputers
Web interface: How to connect to Roihu using the web interface
Disk areas: What places are there for storing data on CSC supercomputers
Object storage: Opening connections to Allas and Lumi-O object storage services
Modules: How to find the programs you need
Applications: Application specific instructions.
Running jobs: How to run programs on the supercomputers
Installing and compiling your applications:
- Installing software
- Compiling on Roihu
Debugging applications: How to debug your applications
Performance analysis: How to understand the performance of your applications
AI Tools: AI Tools provided by CSC