Private-cloud home server setup recommendations

[CC007]

Budget (including currency): €4k (somewhat flexible)

Country: Netherlands

Games, programs or workloads that it will be used for: running a low power, silent, multi-node k8s platform

Other details (existing parts lists, whether any peripherals are needed, what you're upgrading from, when you're going to buy, what resolution and refresh rate you want to play at, etc): 

Right now I have a 3970X threadripper machine with 64GB RAM and 2x2TB storage to run my kubernetes cluster, using Harvester HCI and Rancher. The fact that is a single machine is a single point of failure, so if the machine needs to reboot or requires hardware maintenance, the cluster would go down. Also, the system isn't very quiet and draws quite a lot of power (an amount that is definitely noticable on my energy bill).

I am looking for a different solution, where the server would consist of multiple hardware nodes in a convenient form factor that makes the setup scalable (in case that I need more total processing power) and where I can easily pull out a node for maintenance without bringing down the cluster (on the software side, Harvester and Rancher can help me with that). It would also need to be quiet and draw a small amount of power (relative to the 3970X setup), especially when idle (right now the cpu usage isn't that high yet, but this will probably increase over time). I have heard of blade servers, but I don't know much about them.

I'm not necessarily against a rack mount, considering that I would probably also need a network switch for all the hardware nodes, but I would prefer it to not be too big, especially in the depth direction. Essentially I'm also looking for advice for a rack and network switch to go along with the server pc replacement
 

[CC007]

I found this cute little rack that could probably store it all: https://azerty.nl/product/startech-com-draagbare-server-rack-met-handvaten-rolbare-serverkast/877330
 

I like how it's not too deep and that it has lockable wheels for easy access to the back side when needed. I don't think that I need anything bigger, since 2-5U for compute, 1U for networking and possibly later on 3U for extra separate storage should be enough, right? Also, would the depth be enough for the kind of hardware that I'm looking for?

[CC007]

I have looked a little deeper and if I want to continue using Harvester HCI, it is recommended to at least have 16 cores per system (8 cores minimum, maybe 12 cores should be fine too?) That would mean something akin to 2x a Ryzen 9 3950X or 2x an Epyc 7313 running 3 VMs each (or 3x a ryzen 9 3900x running 2 VMs each). Ryzen seems to be cheaper and lower power.

I also saw a LattePanda sigma, based on an intel i5 12 core mobile processor, but I don't know if there are any server enclosures for it.

Alternatively I could use more light-weight machines, like atom-based machines. I could then still use Rancher, but I would have to run the k8s cluster directly on the machine, rather than in a VM.
Furthermore I could useraspberry pies since the underlying k3s-based k8s cluster can run on ARM (and Rancher has experimental ARM support)

In all these cases, then hardest would be to find rack mounts that could hold these systems (and what motherboards I could user in the case of the Ryzen cpus)

[CC007]

I decided to go for a 10 node pi cluster powered with PoE+ in a 10" wide 12U server rack. I found 2 8-port PoE+ ethernet switches to go along with it.

 

Depending on how good or bad the experience is with Rancher on ARM, I might add a mini-itx case with a ryzen 5600 cpu later.