Noob question: How many guests for 16 cores?

[eugenevdm]

Hi there,

I want to know how many guests I can run on the below configuration please.

I have this CPU:

Model name:          Intel(R) Xeon(R) CPU E5-2620 v4 @ 2.10GHz
Stepping:            1
CPU MHz:             2426.288
CPU max MHz:         3000.0000
CPU min MHz:         1200.0000
BogoMIPS:            4199.93
Virtualization:      VT-x
L1d cache:           32K
L1i cache:           32K
L2 cache:            256K
L3 cache:            20480K
NUMA node0 CPU(s):   0-15

Graphically it's here, I'm using 14 already out of 16.:



My friend recommended to *never* oversell CPU which appear to indicate that I can only have two more vCPUs?

Any advisement?

 

[dylanw]

want to know how many guests I can run on the below configuration please.

This is largely dependent on the tasks of each guest. You should consult the system requirements pages for any operating systems/software you are using.

My friend recommended to *never* oversell CPU which appear to indicate that I can only have two more vCPUs?

I would go one step further than this, and say always undersell, i.e., leave a physical core (2vCPUs in your cpu's case) for Proxmox itself. Otherwise, Proxmox VE may not be able to carry out essentail tasks under heavy load, crashing the system.
It should be noted that you can obviously over-provision cores if not all VMs will be on at once.

 

[eugenevdm]

Ok cool thanks @dylanw , I am deducing that one should never oversell CPUs then.

> You should consult the system requirements pages for any operating systems/software you are using

Some of the workloads are determined by clients to which servers I don't have access so I will have to make the sensible choice for them.

 

[UdoB]

Just another 2 €¢: it completely depends on your workload. For me and my systems the load on the CPUs has never been a problem as most of the VMs are just idling. A Factor higher than 10 is absolutely possible for me.
What I really try to avoid is to over-commit memory. As soon as memory gets into swap space there is no fun anymore.

 

[ph0x]

I would also say that overprovisioning CPUs is usually no big deal, as long as the guests don't burn their vCPUs all at the same time. Since KVM distributes all work on all cores you should just keep an eye that the system load does not get higher than your core count and that IO wait stays low.

 

[spirit]

I'm able to run 200vms (2cores) on a 40cores servers. but (with very small workload by vm)

also, even idle, a vm consume a little cpu for network/disk io polling (maybe 1% of 1 core)