That seagate array will be fine for streaming (so long as you spread the data properly) as soon as you start mixing read/write loads on that, it'll start to chug. You can expect 70-150iops out of each drive, and thats a 60 drive array (from guess, you can get 72 drives in a 4u, but they are less maintainable, well used to be, thing might have improved recently)

When I was using luster with ultra scisi (yes, that long ago) we had good 10-20 racks to get to 100tb, that could sustain 1gigabyte a second.