Ignoring CapacityIQ which I understand isn't yet supported in VSphere currently, I'm trying to develop a logical calculation to estimate capacity in a particular environment. We use an N+1 sizing strategy so, for 2-Quad Core, 32GB memory Hosts, we would max our N+1 memory ceiling and buy another Host before CPU would ever be a concern.

We are now looking at the same amount of cores (2-Quad Core) but increasing to 96GB of memory (HP DL380 G6) so now I'm more concerned with CPU performance. I have heard of some generic VM/Core best practices (4-6 for ESX 3.5) (8-10 for ESX 4.0) however, I'm looking for a more accurate calculation.

Can anyone tell me what metrics I would need to look at and perhaps what calculation I would make to best estimate what kind of CPU capacity I safely have in a paticular Host/Cluster. I'm not even sure if I need to be looking at average MHz over time, vCPU/Core, VM/Core, etc.?

I know there are tools for getting this information like CapacityIQ but, I am trying to "right size" our future Hosts hardware standard.