[bio4m]

If youre on a tight budget and IO is your main bottleneck it may be easier to purchase a number of decent spec desktop PC's with multiple SSD's in them. SSD's have really come down in price while performance and capacity have improved greatly. Same goes for RAM. (Assumption here is that time is less of a concern than cost at the moment and youre not averse to doing some devops work. Also assuming that the processing youre talking about is some sort of batch processing and not realtime) This way you can try a number of different strategies without blowing the bank on AWS instances (and worst case you have a spare workstation)