It being green has nothing to do with it. My WHS is FULL of GP drives, along with other drives.

and it has no problems doing this:

There has been countless arguments on these GP drives. When WD put them out, they said variable RPM 5900-7200, which they did not... They were fixed RPM drives at an unspecified speed. To be quite honest, for a storage drive.... speed doesn't really matter, especially when they can dish out ~100MB/s transfers. The main problem with the GP drive argument is WD hasn't specified too much on them. The instantaneous power on of a hard drive is anywhere from 3-20x of an idle/active drive.(IIRC) That's why we see raid cards with staggered spinups. Either way, when you're pushing 20+ drives in a system, PCI slots become you're most valuable asset. Sure you can get raid cars that support 16+ drives per card, but they tend to be quite expensive. Im quite fond of the Supermicro AOC-SAT2-MV8 cards. At around 100USD for 8 SATA ports, they provide enough connections without breaking the bank. That's why I'm very much into the GB/Sata port thing. The WD 2TB drive I linked is probably slower than the Seagate, but it surely provides a better $/GB ratio and GB/sata port ratio.
Now when someone can link me a 2TB+ SSD drive for around the $150 marker, look out! Ill have to move to a fiber network in my house!
$.02