Read Hit Ratio lower when using ESXi?

Hello,

I’m having a test on my lab comparing Hyper-v 2012 to ESXi 5 performance when running an application that the company I work in developed.

I used to same VM (using the convertor) and the same disks (RDM on VMware and pass-through on Hyper-V) on the same Host ( i switched between the local disks, one with Windows server 2012 and the other with ESXi 5.0).

I’ve seen I’m getting better performance when running on the Hyper-V virtual machine. after analyzing the results I’ve seen that the read cache hit ratio is much higher when I’m running on Hyper-v.

this is probably the reason the application runs better on Hyper-V, it reads a lot from disk. ( I'm using Hitachi's AMS2100 by the way)

anyone had any idea why ESXi uses less cache?