The keyword you want to be searching for is "distributed shared memory"; there s a Wikipedia page on the subject. MOSIX, which became openMOSIX, which is now being developed as part of LinuxPMI, is the closest thing I m aware of; but I don t have much experience with the current LinuxPMI project.
One thing you need to be aware of is that none of these systems work especially well, performance-wise. (Maybe a more optimistic way of saying it is that it s a tribute to the developers that these things work at all). You can t just abstract away the fact that accessing on-node memory is very very different from memory on some other node over a network. Even making local memory systems fast is difficult and requires a lot of hardware; you can t just hope that a little bit of software will hide the fact that you re now doing things over a network.
The performance ramifications are especially important when you consider that OpenMP programs you might want to run are almost always going to be written assuming that memory accesses are local and thus cheap, because, well, that s what OpenMP is for. False sharing is bad enough when you re talking about different sockets accessing a common cache line - page-based false sharing across a network is just disasterous.
Now, it could well be that you have a very simple program with very little actual shared state, and a distributed shared memory system wouldn t be so bad -- but in that case I ve got to think you d be better off in the long run just migrating the problem away from a shared-memory-based model like OpenMP towards something that ll work better in a cluster environment anyway.
