ESX01 is getting more cache hits that ESX2 so this may explain the differences - why it is getting more would be an interesting question.
I tried to make this post clear and concise rather than include details and too much info because I ASSUMED you would realize that I did all the normal background checking and compared not just based on one test, but this was the LAST test I conducted. Therefore my conclusions were based on a series of tests, not one.
For clarification sake I will DETAIL what I did, since apparently you don't see the point I am driving at.
I DID try the switch the LUN's. I did the SAME test the other way by making the VDR point the different LUNs (which is why I chose a Windows file share as the target, so I can make this part easy). I switched the LUNS in the VDR to ensure the VDR themselves were not the choke point or the VM's they were backing up. The results were the same.
so cache hits would NOT matter since they are IDENTICAL configuration. I didn't just merely run a test and go "HERE look what I found". I didn't post this just to quibble over cache numbers and WRITE vs READ IO. Those numbers reflect how each file system (VMFS vs RAW) handles caching, which could be another indication of why there is a difference in performance.
the bottom line is DATASTORE doesn't have the same performance as RAW. Doesn't matter how you spin it or change the parameters, it is what it is.. some posts try to defend VMFS (I was one of them) but I see now (which was the entire point of this) I was wrong.
For people using VDR I thought it might help to improve performance, that was my point. Use RAW as the TARGET in VDR, will dramatically improve performance.