SataPortMap=ABCD
Where A is how many ports on the first HDD/RAID Controller, B the second and so forth.
On the Gen7 HP Microserver, the 1st controller is the onboard RAID (I believe).
If the single onboard SATA port and the rear eSATA port are on the same controller, then it would be SataPortMap=42
If they are seperate controllers, then SataPortMap=411
SataPortMap=4 means first 4 ports of 1st controler.
SataPortMap=44 means first 4 ports of 1st controler and first 4 ports of 2nd controler.
SataPortMap=422 means first 4 ports of 1st controler, first 2 ports of 2nd controler and first 2 ports of 3rd controle
You could try SataPortMap=51 or 411 assuming you have the four bays and the onboard sata port populated and the esata is classed as a separate controller. I'm only using three bays so I can't test the theory.