VMWare ESX 4.1 Settings Disappear on Reboot

I'll chime in here and say that what your engineer was likely talking about is the fact that a VM with multiple vCPU's has a distinct disadvantage when scheduling CPU cycles. A 1 vCPU VM can execute instructions as soon as a single core is available. If a VM has 4 vCPU's, then it literally cannot execute any instructions until 4 cores are available.

If your box has a decent number of VM's on it, this definitely could slow you down b/c your VM will have to wait in line for 4 cores to free up. It could also slow the other VM's down because it will have all 4 cores tied up at once.

I don't want to get into Hyper-Threading and all that, but above is a simple explanation of what I think your guy might have been referring to. Although he may not have done the best job explaining it.

When dealing with people who do not know what they are doing, it is helpful to remember Hanlon's Razor: "Never attribute to malice that which is adequately explained by stupidity."

If you have set up an unattended PXE-based install or some other automatic installation facility for ESXi (e.g. with an inserted CDROM or USB stick), your power cycle might have triggered this for some reason.