we have a cluster consists of 2 ESXi Host with around 90 running VMs and now we have to add 2 old Hosts where we have to activate the EVC mode since the processors are obsolete. Is there any way to enable EVC mode with the VMs running?
Thanks and Regards
No, that's not possible.
Available CPU features are presented to VMs at power on. Since all powered on VMs have to meet the selected EVC level, you cannot select a lower level while the VMs are running.
I believe EVC is a cluster setting, and does not care if VMs are on or off when set. The key thing to remember is that a VM only takes on an EVC setting when it is powered on. So once you have determined the EVC setting you need, you will need to power cycle all VMs that require mobility between hosts with different classes of CPU.
There is a Per-VM EVC setting, but this doesn't sound like something you are going to need.
So for your VCSA, you can set the EVC level and then restart the appliance for the EVC setting to be applied.
>>> if the vcenter server running on the same cluster how we can enable the EVC mode with vcenter vm down?
That can sometimes be tricky, especially without shared storage.
One option that should work, is to configure "Per VM EVC" for the vCSA. For that, create a new, temporary VM with the same compatibility mode (virtual hardware version) as the vCSA, and set the VM's EVC mode to the mode that you want/need to set the cluster to. Then shutdown the vCSA, and append the feature mask settings - the lines that start with "featMask.vm." - from the temporary VM's .vmx file to the vCSA's .vmx file (consider to backup the vCSA's .vmx file prior to that).
Save the vCSA's .vmx file, and reload it (see https://kb.vmware.com/s/article/1026043), then power on the vCSA again.
Now you should be able to set the cluster's EVC mode, if no other VM's are running in the cluster with a higher mode.
Not sure if that is a statement or a question.
As far as I know, changing the EVC setting does not change the state of any currently running VMs, hence the need to reboot them in order for any EVC effects on them to actually take place.
>>> When select the EVC mode through Vcenter console the VMs automatically shutdown
No, definitely not. EVC is just a setting, that can be modified at any time to supported values, which depend on the host's CPU, and powered on VMs.