CERN is the biggest scientific facility in the world, with a huge IT group and their own IXP. Most places are not like that.
Heck, I work at a much smaller particle accelerator (https://ifmif.org) and have met the CERN guys, and they were the first to say that for our needs, OpenStack is absolutely overkill.
> Heck, I work at a much smaller particle accelerator (https://ifmif.org) and have met the CERN guys, and they were the first to say that for our needs, OpenStack is absolutely overkill.
I currently work in AI/ML HPC, and we use Proxmox for our non-compute infrastructure (LDAP, SMTP, SSH jump boxes). I used to work in cancer with HPC, and we used OpenStack for several dozen hypervisors to run a lot of infra/services instances/VM.
I think that there are two things determine which system should be looked at first: scale and (multi-)tenancy. More than one (maybe two) dozen hypervisors, I could really see scaling/management issues with Proxmox; I personally wouldn't want to do it (though I'm sure many have). Next, if you have a number internal groups that need allocated/limited resource assignments, then OpenStack tenants are a good way to do this (especially if there are chargebacks, or just general tracking/accounting).
I'm happily running some Proxmox now, and wouldn't want to got more than a dozen hypervisor or so. At least not in one cluster: that's partially what PDM 1.0 is probably about.
I have run OpenStack with many dozens of hypervisors (plus dedicated, non-hyperconverged Ceph servers) though.
A 'childish set scripts' that manages (as of 2020) a few hundreds of thousands of cores, 7,700 hypervisors, and 54,000 VMs at CERN:
* https://superuser.openinfra.org/articles/cern-openstack-upda...
The Proxmox folks themselves know (as of 2023) of Proxmox clusters as large as 51 nodes:
* https://forum.proxmox.com/threads/the-maximum-number-of-node...
So what scale do you need?