WD Green drives were never designed to be in raid, they are the most awful, slow and failure prone drives I have seen to date. had those darn 1.5TB greens too, had to RMA both of them, and one of them twice (RMA second time) within a month, got rid off them completely, it's junk.
for raid, I'd suggest at least WD Blue or WD Red drives, WD Black will do of course too, it's the fastest of the three and comes in capacities above 1TB, might be just what you need. if you need enterprise class reliability then go with WD RE4 drives, thsoe were designed for heavy duty raid application, they are a bit louder, but pretty much indestructible
Hitachi is a hit and miss sometimes, but I've got one DeskStar (storage drive) and can't complain, it's only 5300rpm, so I use in external USB 3.0 enclosure, it does what it needs to (storing backups).