http://www.allpinouts.org/index.php/Serial_ATA_%28SATA,_Serial_Advanced_Technology_Attachment)
The data cable has three grounds, a TX pair, and an RX pair.
The power cable has 5 grounds, 3 3.3s, 3 5Vs, 3 12Vs, and a reserved.
"Pin 11 can function for staggered spinup, activity indication, or nothing. Staggered spinup is used to prevent many drives from spinning up simultaneously, as this may draw too much power. Activity is an indication of whether the drive is busy, and is intended to give feedback to the user through a LED."
It seems to me that the function would require a backplane or some similar setup to be used and wouldn't be provided by the power supply.