I am currently doing research to determine the consolidation ratio my company could expect should we start using a virtualization platform. I find myself continually running into a dead end when researching how to translate observed performance (weeks of perfmon data) to hdd array requirements for a virtualization server. I am familiar with the concept of IOPs, but they seem to be an overly simplistic measurement that fails to take into account cache, write combining, etc. Is there a seminal work on storage array performance analysis that I'm missing? This seems like an area where hearsay and 'black magic' have taken over for cold, hard fact.