vCenter - vm resources - disk IOPs


I want to know if the IOPs resource tuning is true physical IO operations ?

By this i mean that a series of sequential reads can cause a very high logical read rate while the physical disk accesses can be much lower due to cache buffers at various parts of the system.

e.g. two different senarios

a - sequential reads of some flat file can occur if allowed to run free in the 10s to 100s of Ks, lets say 100 logical to 1 physical

b - random reads or writes that require activity on the disk, lets say 1 for 1

What i am concerned about is if i clamp a vm to have 500 IOPs say, will case a) run slowly ?

The backdrop is we occasionally get a vm sucking all the IO out of our SAN which is shared by vCenter, Lab Manager and vCD, because by default these have
"unlimited" for IOPs


p.s. interested in an KB / whitepaper which covers this in detail

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