Thinking about it more, the best performance would be from a combination of RAMboot with nfs shared tmpfs swapfiles. I put together a how-to on nfs tmpfs swapfile discussed here:
http://www.linuxquestions.org/questi...ap-4175591353/
Basically, if you use nfsroot on tmpfs, then you are bottlenecked by the ~100MB/sec speed of nfs (gigabit ethernet). But if you use the RAMboot technique to put the OS file system in a local tmpfs ram disk, then you get blazing fast speeds. But of course, you're eating up a chunk of your local RAM to do this.
However, less used files will be offloaded to swap. As you run low on RAM, less used files will start to be transferred to swap, freeing up RAM. That takes place at ~100MB/sec. If, later on, you need to access those files, then they'll be loaded back from swap as needed - also at ~100MB/sec. The bottom line is that access for offloaded files is the same speed as the alternative of an nfsroot.
Note that you can have more than one swapfile, so you could use multiple tmpfs swapfiles on different computers. However, to make this work nicely with RAMboot you'll have to do something to make sure the initial OS tarball fits entirely within RAM (less than 8GB). A way to do this is by putting /home into a separate tmpfs file system, that gets loaded separately by /etc/rc.local...
