Thats a Very interesting design and looking at the SD665 V3 documentation am I correct each node has dual 25GBs SFP28 interfaces?
If so, the despite dual nodes in a 1u configuration, you actually have 2 separate servers?
Sid
On Fri, 23 Feb 2024, 22:40 Ole Holm Nielsen via slurm-users, < slurm-users@lists.schedmd.com> wrote:
We're in the process of installing some racks with Lenovo SD665 V3 [1] water-cooled servers. A Lenovo DW612S chassis contains 6 1U trays with 2 SD665 V3 servers mounted side-by-side in each tray.
Lenovo delivers SD665 V3 servers including water-cooled NVIDIA InfiniBand "SharedIO" adapters [2] so that one node is the Primary including a PCIe adapter, and the other is Auxiliary with just a cable to the Primary's adapter.
Obviously, servicing 2 "Siamese twin" Slurm nodes requires a bit of care and planning. What is worse is that when the Primary node is rebooted or powered down, the Auxiliary node will lose its Infiniband connection and may have a PCIe fault or an NMI as documented in [3]. And when nodes are powered up, the Primary must have completed POST before the Auxiliary gets started. I wonder how to best deal with power failures?
It seems that when Slurm jobs are running on Auxiliary nodes, these jobs are going to crash when the possibly unrelated Primary node goes down.
This looks like a pretty bad system design on the part of Lenovo :-( The goal was apparently to same some money on IB adapters and having fewer IB cables.
Question: Do any Slurm sites out there already have experiences with Lenovo "Siamese twin" nodes with SharedIO IB? Have you developed some operational strategies, for example dealing with node pairs as a single entity for job scheduling?
Thanks for sharing any ideas and insights!
Ole
[1] https://lenovopress.lenovo.com/lp1612-lenovo-thinksystem-sd665-v3-server [2]
https://lenovopress.lenovo.com/lp1693-thinksystem-nvidia-connectx-7-ndr200-i... [3]
https://support.lenovo.com/us/en/solutions/ht510888-thinksystem-sd650-and-co...
-- Ole Holm Nielsen PhD, Senior HPC Officer Department of Physics, Technical University of Denmark
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