Client node problems

I have two powerful machines (as I said before) with 32gb ram and a lot of hard disk (i dont remember right now) and I could have an small machine with few ram about 8gb ram and 100gb hard disk but I dont really want to save data in the small machine because I will manage millions of data per day.

Please, could you give a recommendation?
I would like to know if I need a master node or two master nodes, client node, etc for every machine.

Thanks a lot