You can
create any number of VMs as long as you have disk storage to handle them.
Running them simultaneously is another matter. Depends on workload, available RAM, and usually only experimentation will tell.
4C4T you
might get ~5-7 VMs if you go light on vRAM and have at least 16GB on the host.
You need to leave some resources for the host server to do its job (context switching, housekeeping, swapping) and should be prepared to let the guest VMs swap a bit internally. You can try pinning the VMs to certain cores in the GUI or with a script**. And you want everything running on fast + reliable SSD with a decent TBW rating; do
not cheap out on that, or you will run into problems.
**
https://github.com/kneutron/ansites...roxmox-lxc-assign-cpu-cores-6-vcpu--8-pcpu.sh
https://github.com/kneutron/ansitest/blob/master/proxmox/proxmox-vm-assign-cpu-cores.sh
With LXC the math is a bit different, mostly they're idle - so like I said, experiment. If you can get the server running ~80-90% load and still have "acceptable" interactive response at the host console and in-VM, you're doing pretty well.
BUT - we sysadmins are a grumpy and curmudgeonly lot, and some of us tend to
Postulate for Worst Case. If
all of your VMs go active at the same time, are they still getting decent response? If not, maybe downsize the number of running VMs and move some to a different server. Do some stress tests.
Right now my Qotom firewall appliance is ~5.93 load average with 3xLXC and 8xVMs running; it has an 8-core Atom CPU @ 2.2GHz and 32GB RAM. Sensors temp is ~91-95.1'F. Still good response on
ssh and in-vm, and it's running 2x BOINC clients.
GUI response on the Win10/Win11 VMs isn't that great (kinda like working over dialup), but the server only has a stunningly basic VGA-only video chipset, so no 3D accel.
0a:00.0 VGA compatible controller: ASPEED Technology, Inc. ASPEED Graphics Family (rev 30)
^ That's probably literally the cheapest VGA they could throw in for a console, LOL
However, the thing has 4x10Gbit SFP+ ports and 5x2.5Gbit Ethernet ports. And expandable storage options (4-bay disk rack +2x nvme +1xSata-SSD.) And it only pulls ~33 watts running 24/7 - all for under $400
So I have a different (Beelink Ryzen mini-pc) server for GUI-heavy VMs. (The Qotom and Beelink back up to each other with PBS VMs.)
If you need to do more than the current hardware is capable of, sometimes you need to invest in a better potato.
There are a number of Really Good mini-pcs out there these days, and affordable off-lease refurb workstations on e.g. ebay and amazon.
Don't be afraid to ask for recommendations, there's something out there for pretty much every budget depending on what you want to accomplish and how reasonable your goals are.
