Powering a hard drive attached to Raspberry Pi

[bumpy]

First let me say I am not a fan of running power and signal together in a single cable.

Currently I use an external HD connected to my RPI. The interconnect carries only signal and the HD is powered separately from an external power supply.

Now there are some good offers on portable HDs, but they take power from the RPI. Has anyone tried the dual head interconnects that keep the signal and power apart, with the power part plugged into (say) a USB wall socket.

The only one I have found seems to be quite expensive

http://i.ebayimg.com/images/g/LugAAOxys6dSO0LM/s-l500.jpg

http://www.ebay.co.uk/itm/iFi-Audio-Gemini-Dual-Headed-USB-Cable-1-5m-/291784790822?hash=item43efba9326:g:LugAAOxys6dSO0L M

[struth]

My wd my book is self powered. Seems to work well with the pi, and switches its self off when the pi is off after about 10 secs. Dunno if removing the 5v on the usb socket on pi would work but a switch in line may work.