What Seagate drives are you using?
Seagate drives are known for their high failure rate.
http://wikipedia.org/wiki/Seagate_Barracuda?title=Seagate_Barracuda&seg=2&useformat=
I find that all drives have a failure rate, this is especially higher when it comes to those I use.
All are equally unreliable these days. Need one drive, purchase two is my motto now... the cheaper the better. I hate technology.