When your 500GB "disk" is directly addressable on the system bus and has the same latency as RAM, some of the design decisions in existing *nix look a bit questionable. Example: Does the additional work of implementing virtual memory (fundamental to most kernels) still make sense? How necessary is a file system *at all*? Could it be replaced with some other method of indexing data?
You certainly could just stick most of the storage in a ramdisk and run linux, but there might be massive performance gains to be had in the file (data?) serving and database spaces if the server software and the kernel it's running on are designed specifically for stable direct addressing of everything.