We have an application (Finance1) that we are looking to deploy within our network. As is our current strategy for most things, we will deploy the app on VM ESX 3.5 guests rather than physical boxes.
The vendor has various performance calculators, hardware calculators, storage calculators to gauge the hardware necessary to run Finance1. We enter in data for some fields related to usage (number of users, level of activity they are carrying out etc) and also the hardware specs of the machine (physical memory, CPU types etc) and the calculators will provide info back on whether this would work adequately or not.
Problem is, their calculators are all based on physical servers not virtual ones. I'm going to get back to them and ask them, but in the meantime I was wondering - should this sort of calculator apply to both physical and virtual servers? Or do VM guests' resources have an overhead for running as VM's (e.g. some percentage of resources being eaten up by the host etc) that would make them not accurate?