I ran an OpenMOSIX cluster as a hobby. The alternative was Beowulf (the meme of the day was "Imagine a Beowulf cluster of these things").
It seems the mainstream server industry has moved to more isolation rather than more interconnectedness, which is probably better for most public-facing systems.
Isolation is orthogonal to what I listed. MOSIX has decent sandboxing. I don't know about Linux-PMI or OpenMOSIX, though. They died off years ago anyway.
It seems the mainstream server industry has moved to more isolation rather than more interconnectedness, which is probably better for most public-facing systems.