Effects of scale Want to scale by addition of equally powerful servers. Should be able to calculate how many servers you need. Server load should not scale with overall size of the system. Increased growth might imply 3 level naming hierarchy. Since messages are shared on a server, want servers to map to communication units.
System load gets too heavy.
Haven't tried it, but consider splitting registry and message servers across two machines. Assigning secondary inboxes is hard. Don't want to overload secondary on failure. Still want to get sharing of messages. Want to avoid problems with unreliable links.