To read the HDD and serve up media while in sleep mode has yet to be done.

HOWEVER I did this another way and I'll share. My router has 2 USB ports that I can plug in some HDD (low power) and USB MEMORY sticks and it can serve up files or DLNA (see google).

Then my PC can be off or sleep and the media is shared. Just last week I upgraded the USB HDD to a 2TB Toshiba Canvio Basic since I didn't want the "extras" in the other models. Also I wanted it to be low power and big.

PS. Added with edit.
I used the 80 buck model at http://www.amazon.com/Toshiba-Canvio-Basics-Portable-HDTB220XK3CA/dp/B00ARJD56K