Parking heads that many times a day is not good... Also spinning down and up and down and up will kill a drive faster than leaving it spinning 24x7x365.
When it comes to raid or nas don't cheap out... At least buy regular desktop drives, forget about the green drives. If it's mission critical data then invest in enterprise class drives, although you probably wouldn't do so unless you were running a more expensive / higher performing raid or nas.
Posted via RS Mobile