Not enough CPU capacity

[SirHaschke]

Hi,
we have a VM with 12 CPUs and a reservation 21800 MHZ.

If i try to set it to 16 CPUs with reservation 35000 MHZ i get this error:

We use 2 Servers in the cluster with this HW:

Why can't i set a reservation with 35000 Mhz?

Regards

Dennis

[berndweyand · Accepted solution]

because 2.1 * 16 = 33600 MHz - try that number

[scott28tt]

What is the VM doing to warrant 16 CPUs with a full reservation?

[a_p_]

How many VMs are running on that cluster, and how is HA (Admission Control) configured?

You may see whether the VM starts with HA being disabled, to find out if it's a configuration issue?

André

[SirHaschke]

bewe​

Ah, ok. And if i take 18 Proc. then i can set an reservation from 37800 MHz.....

scott28tt​

This is a conferencing system from our telephone system.
The manufacturing company has this as System requirements.

a.p.​

ca. 40 VMs on 2 physikal ESXi servers.
HA is Active, but only Active for one VM because the other VMs are created redundantly.
The phone manufactor have an own HA.

[scott28tt]

Those "requirements" may be intended more for physical than virtual environments - you may find that performance is acceptable with fewer CPUs for the VM, in fact it may even be better given how easier it makes things for the ESXi CPU scheduler.

I would definitely recommend testing the app to see what CPU resources are REALLY needed.

[a_p_]

Interesting that some of the phone/conferencing system providers still seem to have no clue about how virtualization works.

Anyway, with the defaul HA settings, vSphere calculates minimum slot sizes based on the highest reservation on any of the VMs. These minimum slot sizes are then assumed for each powered on VM, that's why HA refuses to power on the VM.

Options are:

• if the vendor insists on VM reservations, then either reconfigure Admission Control from the default settings, to percentage settings, or set fixed slot sizes (CPU, and RAM) with smaller values, e.g. 256MHz, and 256MB.
• other than this, creating a Resource Pool for this one VM, and configure the reservations on the pool, rather than on the VM itself should work too.

André