Frequently asked questions about Roihu

Roihu is now in active use. See getting started tutorial for Roihu and more information on Roihu.

Frequently asked questions about Roihu

Mahti/Puhti shutdown

1. When will Puhti/Mahti be shut down?

Puhti compute resources will be shut down one month after Roihu general availability, by 31 July 2026. After this, jobs can no longer be submitted on Puhti. Puhti storage and login nodes are planned to remain accessible until 15 October 2026.

Mahti compute resources will be shut down on 31 August 2026. Mahti storage and login nodes are planned to remain accessible until 15 October 2026.

We strongly encourage users to move any required data by the end of August 2026, as Mahti and Puhti storage services will not be covered by service contracts between September and October, and availability cannot be fully guaranteed.

2. I heard that Puhti will be donated for continued use. Can I apply for hardware?

The application deadline was in March 2026 and has now passed.

Accessing Roihu

3. Will logging in to Roihu be different than for Puhti/Mahti?

In addition to SSH keys, a signed SSH certificate is required to connect to Roihu over SSH.

Read the instructions for getting and using SSH certificates here.

Short talk: SSH authentication changes to Roihu

4. Is there a web interface for Roihu like Puhti and Mahti have?

Yes. The Roihu web interface provides easy access to the computing and storage resources of Roihu. Like the web interfaces for Mahti, Puhti and LUMI, the Roihu web interface is particularly aimed at interactive workloads and running graphical applications like Jupyter Notebooks, RStudio, etc.

Roihu web interface is available at www.roihu.csc.fi, similarly to Mahti, Puhti and LUMI.

See documentation on the Roihu web interface.

5. My terminal looks weird when logging in to Roihu

When you log in to Roihu in your terminal, you should see a "Message of the Day" (MOTD), similarly to Mahti, Puhti and LUMI, providing you with useful information about the system.

The Roihu MOTD may use characters or symbols that are not supported by all terminal fonts. If the required fonts are missing, the MOTD may look visually broken, show placeholder boxes, or have other visual glitches.

This will not affect your Roihu session or your work, and it can be safely ignored.

Migrating to Roihu

6. Will current CSC accounts and projects be automatically migrated to Roihu? How do I add Roihu as a service?

CSC accounts and projects are not tied to specific services. In other words, the same CSC account and projects can be used for different CSC services, including Roihu.

You can add Roihu as a service to your existing project(s) in MyCSC, similarly to Puhti or Mahti. The existing billing units in your project can be used on Roihu. Scratch/projappl space will be created to your project to Roihu automatically after applying, but data is NOT transferred automatically from Mahti or Puhti.

To be able to use Roihu, you will need to add Roihu service access for your project.

Additionally, you should have at least a medium level of identity assurance (LoA) to be able to access Roihu, i.e., you need to have been authenticated with strong authentication. You can view your current level of identity assurance in MyCSC (select Profile and scroll down to Level of Identity Assurance).

Users with no or low LoA should read the instructions on how to elevate their assurance level.

7. Are existing disk quota extensions on Puhti/Mahti automatically applied on Roihu as well?

No, all projects will start with default quotas. Any quota extensions must be applied for separately and the needs properly motivated.

Storage BUs from an existing project can be used, when you add Roihu as a service into that project.

The default disk quotas in Roihu are as follows:

	Capacity	Number of files
home	15 GiB	150 000 files
projappl	15 GiB	150 000 files
scratch	250 GiB	500 000 files

Do note that the default quotas in Roihu are more restrictive than on Mahti and Puhti. Only apply for more quota if you strictly need to.

See documentation on increasing disk quotas.

8. Will users' data be automatically migrated to Roihu? How should I migrate my data from Puhti/Mahti?

No, users will have to move their data to Roihu themselves, if needed.

With data migration, the main take-home message of the guide is to only move data that you truly need. Dumping everything from Puhti and/or Mahti scratch to Roihu "just in case" is not acceptable. Roihu will implement a similar data cleanup cycle as Puhti and, as stated above, prior quota extensions on Puhti and/or Mahti will not be carried over to Roihu.

Migration of data should primarily happen directly from Puhti/Mahti to Roihu, between July and August 2026. Mahti and Puhti storage will be fully shut down 15 October 2026.

See the detailed schedule of Puhti and Mahti shutdown in the Roihu docs page.

See the data migration guide, for how you can move data directly from Mahti and Puhti to Roihu.

Short talk: Roihu data migration tips:

9. Do I need to migrate data from Allas to Roihu?

Allas is not affected in this update. You can keep your current data there. If you have your data in Allas, you can access that data from Roihu too. That data does not need to be migrated, as Allas will remain available during and after the Roihu transition.

It is not recommended to transfer data from Mahti/Puhti to Roihu via Allas or your local workstation. Instead, CSC recommends using command-line based tools such as rsync to directly transfer data from Puhti/Mahti/LUMI to Roihu.

10. How should I run large or long-running data transfers, and how long do they take?

It is ok to use rsync on the Mahti/Puhti login nodes. Please read the data migration guide carefully, and consider compressing your data before transferring it, to save time and resources used in the migration. Only move data that you truly need.

For long transfers, use screen or tmux on Mahti/Puhti so the transfer is not interrupted if your connection drops. See the guide for running long transfer processes safely, or our tmux usage tutorial.

Transfer times depend on the amount and size of files: large numbers of small files take longer, so consider archiving them into a single file first. As a ballpark, a single ~100 GB file takes about 10 minutes to transfer directly between the systems.

11. I have multiple projects in Mahti and Puhti. Should I move data for each project individually?

You can add Roihu as a service to each project individually. Data transfer can be done on a project-by-project basis, so the answer really depends on your workflow. If multiple projects need access to the same data, you might be interested in the new "Dataset project" service, where you can apply for a special disk area for storing data that multiple (or all) projects on the system can access.

Roihu hardware and software

12. What kind of hardware does Roihu have?

See the Roihu system description for details.

Notably, Roihu has different CPU architectures on the AMD Turin-based CPU nodes (x86) and NVIDIA Grace-Hopper GH200-based GPU nodes (ARM). Accordingly, there are also two different login node flavors for users targeting the CPU or GPU partitions, respectively:

roihu-cpu.csc.fi (x86, AMD Turin), and
roihu-gpu.csc.fi (ARM, NVIDIA Grace)

Software built on the x86 login nodes will only run on the CPU compute nodes, while software built on the ARM login nodes will only run on the GPU nodes. Similarly, CPU and GPU Slurm jobs can only be submitted from the x86 and ARM login nodes, respectively.

13. What operating system does Roihu have?

The operating system of Roihu is Red Hat Enterprise Linux (RHEL) 9.

14. Is Tykky available on Roihu?

Yes, Tykky (tool for creating containerized Conda etc. environments with wrapper scripts) is also available on Roihu.

15. Sensitive data and Roihu: What is the Roihu-integration with SD Desktop and how will it work?

Roihu will eventually support a secure workflow for sensitive data processing. The technical implementation will include the capability to submit jobs from the SD Desktop to Roihu. However, setting up the workflow specific for secure sensitive data processing service for Roihu will take several months. As a result, this functionality is expected to become available only towards the end of 2026 or the beginning of 2027.

16. Is there a list of pre-installed software/modules available?

Yes, a list of installed software is available in the application section. The goal is to provide the same software as on Puhti and Mahti as far as possible, with some necessary changes such as version numbers and module names, for example pytorch -> python-pytorch. Some older and less used module versions may be deprecated. Most applications work very similarly to Mahti and Puhti, for example, Python and R usage and including new libraries is almost identical to Roihu.

Some commercial software for which the vendor does not provide ARM (aarch64) support will not work on the Roihu GPU side, as it uses the NVIDIA Grace ARM CPUs. Examples previously installed on Puhti/Mahti include Desmond and CryoSPARC. We're working to provide alternative ways for users to use those software.

Missing software can be requested from CSC by contacting the CSC Service Desk. If there is enough demand, we will consider creating a system-wide installation, but we cannot promise to install everything that users might want.

Installing and running software on Roihu

17. Do Roihu's Slurm partitions have the same memory/time limits as on Mahti and Puhti?

There are some differences in the available partition names and the corresponding hardware, when compared to Mahti and Puhti.

You can see the available partitions and the corresponding limits in the Slurm partition documentation for Roihu.

18. Does Roihu have a longrun partition? What is the maximum runtime?

There is a longrun partition on Roihu. The maximum time for a job in the Roihu longrun partition is 10 days. The small partition for partial or single nodes has a time limit of 72 hours.

19. NVMe, temporary storage and local scratch in Roihu

All Roihu compute and login nodes provide temporary local NVMe storage through $TMPDIR. Unlike on Puhti and Mahti, it does not need to be requested with --gres=nvme, and $LOCAL_SCRATCH should not be used as a direct replacement. Any existing job scripts using local NVMe storage on Puhti and Mahti will need to be updated for Roihu, to use Roihu's $TMPDIR, or other local storage options instead.

The available capacity depends on the node type, and additional temporary NVMe storage can be requested for some jobs.

See the Roihu temporary local storage documentation for capacities and usage instructions.

20. I did not find an answer to my question here. Who should I contact?

Please send email to CSC Service Desk. We are happy to help!