Cluster Capacity

[Gcm11]

Hi ppl,

Have a query on ESXi  cluster capacity.

I have a cluster with 3 ESXi.
Each server is with 4 CPUs @22 Cores @2.1Ghz with HT

Total vCPUs assigned to VMs= 629

For now, I can isolate 1 ESXi for maintenance. As the environment is growing, will need to deploy new VMs with estimate of 200 vCPUs.

How can I calculate the CPU usage to ensure I still have the capacity to isolate 1 ESXi for maintenance? Is there any forumlas or tools to achieve the calculations?
Objective is not to shutdown any VMs during ESXi maintenance.

[a_p_]

I'm afraid that there's no rule of thumb for that, as it depends on the VMs' workload.
Best bet might be to look at the current resource/CPU usage, and make an estimation.

André

[Gcm11]

Hi Andre,

Thanks for the reply. We are running a shared infra for hosting the VMs, we do not know the actual load. Request just comes in to request for new VMs.

Will want to make sure the cluster has sufficient capacity to manage before we commit the deployment.

We do not want to run into a situation where we need to request VMs to be shutdown to perform ESXi maintenance.

[scott28tt]

You need to understand utilisation, not just think about the number of vCPUs.

[ck1489]

Please go through below to understand vCPUs, usage is what matters in your scenario. Until or unless you have vRealize or some other tool for Capacity management.

https://docs.vmware.com/en/VMware-vSphere/7.0/com.vmware.vsphere.vm_admin.doc/GUID-3CDA4DEF-3DE0-4A6...

[Gcm11]

Hi Scott,

I can see the current cluster utilization, but when requests comes in, they will just request with eg. 5 VMs with 10vCPU and 24GB RAM. Most requesters do not know their utilizations.

Thus, will need to calculate if the cluster can manage with the new loads before we even deploy.

[Gcm11]

Hi CK,

We do not have vRealize, thus looking any free 3rd party tools or manual calculations, using excel etc to estimate even before we commit to deploy new VMs.

We usually just get request eg. to deploy a VM with 4vCPU and xx RAM or 5 VMs with 10vCPU 24GB RAM. Most requesters will not know the utilization.

We do not want to over provision and hit with resource issues.

[Gcm11]

Sharing a link from VMware support

https://github.com/danbarr/capacity-planning