Intel Xeon Bronze 3104 and Virtualization? How Many VMs at Once?

I realize this is a subjective question depending on what the VMs are, but I’m completely unfamiliar using Xeons, so I’m not sure what to expect.

I’m planning to run Proxmox as my hypervisor, since I’m using it on other nodes already.
I’m almost certainly going to set up a TrueNAS Core VM to run the spinning drives (again, I already a TrueNAS instance running, so I’m planning to use clustering/replication features built into it).

How many VMs/CTs should I expect to be able to run at once with TrueNAS being the one that has to run all the time?

I’m expecting to hit a ceiling with 16GB of RAM before I run into CPU resource issues, but I have no idea how to estimate resource usage on this type of system.

(My other nodes are (1) an Intel Celeron N6005, and (2) a Ryzen 8C16T 3700X.)

This is a pretty common question, and one that doesn’t have a definitive answer. The true answer is “It depends”. It depends on your VM’s, Docker containers, their resource consumption, etc.

Before we dive any further, a Xeon chip is not very different from a standard Intel CPU. In fact, some sockets and motherboards in servers or workstations can support both a Xeon model or an i3. Xeon typically is more feature rich with things such as ECC support, larger and faster cache, etc. but usually do not have iGPU. In the Enterprise side of the world, there would be almost no want or need as many run headless or support display through virtualization.

I just skimmed this post from the Proxmox forums here. Granted, I did not read the entirety, but it seemed to line up with best practices we follow for VMware ESXi.

1vCPU = 1 Physical core.

There is an argument that’s as old as time on what a “Core” is, either physical core or hyperthreading, but I’ve always stuck with physical to play it safe. The 3104 is also non Hyperthreaded as well, so in this case it’s easy to pick your camp. If you oversubscribe your resources, you will have a bad time as the hypervisor itself (Proxmox in your case) still needs CPU resources to handle all those guest VM’s and any virtual networking you have going on.

I also agree that the 16GB of memory will be your first limiting factor. If you plan to use ZFS, it uses Memory for ARC cache, placing your Reads and Writes there to allow for a large performance gain. So, needless to say, ZFS alone will want a slice of the pie.

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what a “Core” is

I’ve had trouble with my proxmox setup overcommitting its resources, depending on the work you do you may or may not benefit from hyperthreading

Rule of thumb seems to be:

1 core with 2 threads == 1.25 cores

Anecdotally, having lowered the vCPUs on one of my heavy duty work VMs actually did improve performance, in my case. YMMV