The Power Over eSATA port combines eSATA and USB and enables the power supply of 5V via the integrated USB interface.
Thus you do not require any additional power supply for a 2,5” HDD.
Connection: Power Over eSATA (eSATAp) > SATA 22pin + 4pin Molex
Cable length: 50cm
For operation of a 3,5” HDD just connect the Molex-connector to a power supply.