Hans-Nikolai Viessmann
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Introduction
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About Merlin7
PSI's Merlin7 cluster is run on top of an IaaS (Infrastructure as a Service) vCluster on the CSCS Alps infrastructure. It is fully integrated with the PSI service landscape was designed to provide the same end user experience as its PSI-local predecessor clusters.
Merlin7 has been in production since beginning of June 2025.
All PSI users can request access to Merlin7, please go to the Requesting Merlin Accounts page and complete the steps given there.
In case you identify errors or missing information, please provide feedback through merlin-admins mailing list mailing list or submit a ticket using the PSI service portal.
Infrastructure
Hardware
The Merlin7 cluster contains the following node specification:
| Node | #N | CPU | RAM | GPU | #GPUs |
|---|---|---|---|---|---|
| Login | 2 | 2 AMD EPYC 7742 (64 Cores 2.25GHz) | 512GB | ||
| CPU | 77 | 2 AMD EPYC 7742 (64 Cores 2.25GHz) | 512GB | ||
| GPU A100 | 8 | 2 AMD EPYC 7713 (64 Cores 3.2GHz) | 512GB | A100 80GB | 4 |
| GPU GH | 5 | NVIDIA ARM Grace Neoverse v2 (144 Cores 3.1GHz) | 864GB (Unified) | GH200 120GB | 4 |
Network
The Merlin7 cluster builds on top of HPE/Cray technologies, including a high-performance network fabric called Slingshot. This network fabric is able to provide up to 200 Gbit/s throughput between nodes. Further information on Slignshot can be found on at HPE.
Through software interfaces like libFabric (which available on Merlin7), application can leverage the network seamlessly.
Storage
Unlike previous iteration of the Merlin HPC clusters, Merlin7 does not have any local storage. Instead storage for the entire cluster is provided through a dedicated storage appliance from HPE/Cray called ClusterStor.
The appliance is built of several storage servers:
- 2 management nodes
- 2 MDS servers, 12 drives per server, 2.9TiB (Raid10)
- 8 OSS-D servers, 106 drives per server, 14.5 T.B HDDs (Gridraid / Raid6)
- 4 OSS-F servers, 12 drives per server 7TiB SSDs (Raid10)
With effective storage capacity of:
- 10 PB HDD
- value visible on linux: HDD 9302.4 TiB
- 162 TB SSD
- value visible on linux: SSD 151.6 TiB
- 23.6 TiB on Metadata
The storage is directly connected to the cluster (and each individual node) through the Slingshot NIC.