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# Technical details about Puhti

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

    Puhti computing services have been shut down 31 July 2026 at 12:00 EEST, and
    no new jobs are accepted or executed on its compute nodes.

    Storage and
    login nodes are planned to remain accessible until midday 15 October 2026, but
    users are strongly encouraged to move any required data from the system
    by the end of August 2026.

    [Learn more about Roihu :material-arrow-right:](systems-roihu.md)

## Compute

**Puhti** has a total of **682 CPU nodes**, with a theoretical peak
performance of 1,8 petaflops. Each node is equipped with two Intel
Xeon processors, code name _Cascade Lake_, with 20 cores each running
at 2,1 GHz. The cores support AVX-512 vector instructions and VNNI
instructions for AI _inference_ workloads. The interconnect is based
on Mellanox HDR InfiniBand. The
nodes are connected with a 100 Gbps HDR100 link, and the topology is a
fat tree with a blocking factor of approximately 2:1.

The **Puhti AI** artificial intelligence partition has a total of **80 GPU
nodes** with a total peak performance of 2,7 petaflops. Each node has
two Intel Xeon processors, code name _Cascade Lake_,
with 20 cores each running at 2,1 GHz. They also have four Nvidia
Volta V100 GPUs with 32 GB of memory each. The nodes are equipped with
384 GB of main memory and 3,6 TB of fast local storage. This partition
is engineered to allow GPU-intensive workloads to scale well across
multiple nodes. The interconnect is based on a dual-rail HDR100
interconnect network connectivity providing 200 Gbps of aggregate
bandwidth in a non-blocking fat-tree topology.


## Nodes


| Name      |  Number of nodes |  Compute       | Cores                  | Memory  | Local disk |
|-----------|------------------|----------------|------------------------|---------|------------|
| M         |  484             | Xeon Gold 6230 | 2 x 20 cores @ 2,1 GHz | 192 GiB |            |
| M-IO      |  48              | Xeon Gold 6230 | 2 x 20 cores @ 2,1 GHz | 192 GiB |  1490 GiB  |
| L         |  92              | Xeon Gold 6230 | 2 x 20 cores @ 2,1 GHz | 384 GiB |            |
| L-IO      |  40              | Xeon Gold 6230 | 2 x 20 cores @ 2,1 GHz | 384 GiB |  3600 GiB  |
| XL        |  12              | Xeon Gold 6230 | 2 x 20 cores @ 2,1 GHz | 768 GiB |  1490 GiB  |
| BM-IO     |  6               | Xeon Gold 6230 | 2 x 20 cores @ 2,1 GHz | 1,5 TiB |  5960 GiB  |
| GPU       |  80              | Xeon Gold 6230<br>Nvidia V100  | 2 x 20 cores @ 2,1 GHz<br> 4 GPUs connected with NVLink | 384 GiB<br>4 x 32 GB |  3600 GiB  |

In addition to the compute nodes above, Puhti has two login nodes with 40 cores and 2900 GiB
[local disk](disk.md#login-nodes) each.


## Storage

Puhti has a 4.8 PB Lustre parallel storage system providing space for
[home](disk.md#home-directory), [project](disk.md#projappl-directory) and
[scratch](disk.md#scratch-directory) storages.

Current Lustre configuration for Puhti is:

| Storage area | # OSTs | # MDTs |
|--------------|--------|--------|
| home         |  24    |   4    |
| projappl     |  24    |   4    |
| scratch      |  24    |   4    |

Please see [Lustre documentation](lustre.md) for the terminology.

All the OSTs and MDTs are shared across the storage areas, thus the
performance should be similar between them. The peak I/O performance
in Puhti is around ~50 GB/s with 64 compute nodes under dedicated
access to the system.
