HDD for Sony HX85x Tv??

I just got a Sony 46HX850 Tv, and connected a spare LaCie USB HDD that I happened to have lying around. With it, the recording function "pause Tv" works fine when the Tv is on. But if I program the Tv to record something in the future and turn off the Tv, then the recording fails and the Tv error log give a message something like "HDD not available". I think the HDD may be going to sleep when the Tv is off, and not waking up fast enough when the recording needs to be done. Is there anything I can do to solve this? Or do I need to buy a new HDD? And if so, what models are known to work?