Using Ubuntu Enterprise Cloud, how do I estimate the CPU capabilities that my VMs can have based on the server CPU?
Let's say that I have a Intel Xeon X3440 ( http://ark.intel.com/products/42928 ). How many single core 1.5 GHz VMs can I run there?
Completely dependent on what each of those VMs is actually doing on a per-second basis. If they're all ticking over and doing very little, you can potentially run hundreds of VMs on a single chip (up to the configuration maxims of your chosen hypervisor).
On the other hand if you have a few beastie CPU hog VMs, it won't be long before performance suffers across the board. You can mitigate that by ringfencing resources for VMs or groups of VMs. However, you're still ultimately bound to a division of the total performance of the chip.