# Systems

!!! warning "Puhti and Mahti retirement in 2026"
    Puhti and Mahti will be decommissioned in 2026 and replaced by Roihu, CSC's
    next-generation supercomputer offering enhanced performance and
    capabilities.

    * Puhti computing services have been shut down since 31 July 2026.
    * Mahti computing services will be shut down 31 August 2026 at 12:00 EEST.
    * Puhti and Mahti storage and login nodes are planned to remain accessible until 15 October 2026 at 12:00 EEST.
    * Users are strongly encouraged to move any required data from these systems by the end of August 2026, as storage access cannot be fully guaranteed after that.

CSC's computing environment consists of supercomputers Roihu, Puhti and
Mahti. Puhti and Mahti have a
fairly similar compute environment, and there is a wide range of
workloads that can utilize both efficiently. At the same time their
hardware is different, and this makes some workloads uniquely suitable
for either Puhti or Mahti.

Mahti and Puhti are being decommissioned over the summer 2026, with their storage services shutting down 15 October 2026.
Puhti's compute services have been shut down, and no new jobs will be accepted or executed on its compute nodes.

In addition to the national supercomputers, CSC's data center in Kajaani hosts the
pan-European pre-exascale supercomputer LUMI. The CPU-partition of LUMI has
been available since early 2022, while the largest partition of the system
consisting of GPU-accelerated nodes became available in 2023.

## Roihu

The Roihu supercomputer, BullSequana XH3000 hybrid system, is CSC's next
national supercomputer and is replacing Puhti and Mahti over the summer, in 2026.
Roihu is designed as a versatile system for CPU and GPU computing, AI workloads,
data-intensive research and applications requiring large memory.

Roihu consists of two main partitions: **Roihu-CPU** and **Roihu-GPU** that have separate login nodes
and software environments. The CPU partition contains AMD EPYC
CPUs, while the GPU partition is based on NVIDIA GH200 Grace Hopper Superchips.
The system also includes special-purpose nodes for visualization and high-memory
tasks, and will provide enhanced support for processing sensitive and confidential data.

- [More information about Roihu](systems-roihu.md)

## Puhti

The Puhti supercomputer, Atos BullSequana X400 cluster based on Intel
CPUs, was launched on September 2, 2019. It had a powerful CPU
partition with almost 700 nodes with a range of memory sizes and local
storage options, all connected with a fast interconnect. Puhti allowed
the user to reserve compute and memory resources flexibly, and the
user could run anything from interactive single core data processing to
medium scale simulations spanning multiple nodes.

There were also 80 GPU nodes, with total of 320 Nvidia Volta V100 GPUs. This
partition was suitable for all kinds workloads capable of utilizing GPUs, even
heavy AI models that span multiple nodes.

Puhti provided a wide selection of [scientific software](../apps/by_availability.md#puhti)
installed.

- [A more technical description of Puhti](systems-puhti.md)

## Mahti

The Mahti supercomputer, Atos BullSequana XH2000 system based on AMD
CPUs, was launched on August 26, 2020. Mahti is designed for
massively parallel jobs requiring high floating point performance and
a fast interconnect. The system has in total 1404 nodes equipped with
powerful AMD Rome CPUs. These are connected with a fast interconnect,
allowing jobs to scale across the full system. In Mahti user reserves
full nodes so that the jobs can extract full performance from each
node. Mahti is in particular geared towards medium to large scale
simulations requiring Petaflops of compute power. Also smaller
parallel workloads that are able to use full nodes efficiently can
utilize Mahti.

There are also 24 GPU nodes, with total of 96 Nvidia Ampere A100 GPUs. This
partition is suitable for all kinds workloads capable of utilizing GPUs, even
heavy AI models that span multiple nodes. A subset of the A100 GPUs are sliced
into smaller GPUs with one seventh of the compute and memory capacity of a full
A100 GPU. These can be used for interactive workloads, courses and code
development.

The selection of installed [scientific software](../apps/by_availability.md#mahti) in
Mahti is more limited than in Puhti.

- [A more technical description of Mahti](systems-mahti.md)

## LUMI

LUMI is one of the three European pre-exascale supercomputers. It's an HPE Cray
EX supercomputer consisting of several partitions targeted for different use
cases. The largest partition of the system is the "LUMI-G" partition consisting
of GPU accelerated nodes using a future-generation AMD Instinct GPUs. In
addition to this, there is a smaller CPU-only partition, "LUMI-C" that features
AMD EPYC "Milan" CPUs and an auxiliary partition for data analytics with large
memory nodes and some GPUs for data visualization. Besides partitions dedicated
to computation, LUMI also offers several storage partitions for a total of 117
PB of storage space.

- [LUMI user documentation](https://docs.lumi-supercomputer.eu/)
- [A more technical description of LUMI](https://docs.lumi-supercomputer.eu/hardware/)
- [How does LUMI-C differ from Mahti?](lumi-vs-mahti.md)
