While building out a UC infrastructure for a customer, I noticed recently that the requirement for an extra core when installing Unity Connection is dropped with ESXi 5.5+. In order to qualify to do this, you have to set the Latency Sensitivity for the Unity Connection VM to high.
The problem I had with this is I could NOT find out how to do this if you are running ESXi only (no vCenter). Turns out it can be done, but it's not well documented yet.
1. Make sure the VM is "OFF"
2. VM ==> Edit Settings ==> Options ==> Advanced ==> General
3. Hit the configuration button.
4. Look for the the named parameter: sched.cpu.latencySensitivity, if you don't see it, hit the add row button and add it.
5. Set the value = high
Click OK and Ok to get back out.
Hopefully this will save some others the time I wasted trying to find it. I was pointed to an online blog by WarCop you can find here: http://blog.warcop.com/2015/05/04/cisco-uc-and-vmware-latency-sensitivity/ ;
This solved my issue!