tom thumb said:
If it scaled perfectly, you'd get ~800 read and 300 write.
To be realistic, perfect scaling requires all of the I/Os to be issued on exactly the right sectors at exactly the right times. You can get it in a benchmark program designed to do that, but you'll never achieve it in real life.
You also have to consider that even though RAID can increase transfer rates, it really doesn't improve the access times - so performance that depends on random I/Os doesn't really improve much at all.