It's best to use five flash drives plugged directly into the PC supplying only 100 MB to 200 MB each on a USB port.
I was running 512 MB RAM with Ubuntu Linux, and that ran smoothly playing Minecraft. But even if you have more RAM, but need more, that's the way to go for best performance, because USB ports are so fast, 200 MB to 500 MB or more, but if you put a lot of RAM on just one of those loads, it's going to lag.
With multiple USB sticks with small RAM loads, you'll experience less lag and maybe RAM speed, highly suggest turning off the RAM load for hard drive when doing this because the hard drive has a write speed of 20 MB, not very fast.