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Puhti and Mahti are CSC's supercomputers. Puhti has been available for CSC users since 2 September 2019 and Mahti has been available since 26 August 2020.

Puhti contains CPU nodes with a range a memory sizes as well as a large GPU partition (Puhti AI), while Mahti contains homogeneous CPU nodes and is meant for larger jobs (minimum 128 CPU-cores). See specifications for details on the systems.

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

Accessing Puhti and Mahti

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

Connecting to the supercomputers

Connect using a ssh client:

ssh <csc_username>


ssh <csc_username>

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

ssh <csc_username>@puhti-login<number 1-2>


ssh <csc_username>@mahti-login<number 1-2>

For more details, see the connecting page.

Usage policy

When you login to CSC supercomputers, you end up to one of the login nodes of the cluster. These login nodes are shared by all users and they are not intended for heavy computing.

The login nodes should be used only for:

  • compiling
  • managing batch jobs
  • moving data
  • light pre- and postprocessing

Here light means one-core-jobs that finish in minutes and require a few GiB of memory at maximum. All the other tasks are to be done in compute nodes either as normal batch jobs or as interactive batch jobs. Programs not adhering to these rules will be terminated without warning.


The login nodes are not meant for long or heavy processes.

Projects and quotas

Working in Puhti 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 with MyCSC portal, were you can add services, resources and users to your CSC projects.

In Puhti, you can check your currently active Puhti-projects with command:


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

[kkayttaj@puhti ~]$ csc-projects -p project_2012345
Project: project_2012345    Owner: Kalle Käyttäjä
Title: "Ortotopology modeling"
Start: 2015-12-17 End: 2022-03-16 Status: open
Budget:   1174188  Used   1115284 Remain:      58904
Latest resource grant: 2019-03-04

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 have been granted to your project, how much has been used and how much still remain.

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


Check Disk areas chapter for details.

Using Puhti and Mahti

Last edited Fri Oct 30 2020