Concerning overall performance on a server that is solely running Zimbra in an environment where almost all users are Web Interface users and the per-user mail volume is low to moderate.

How well does it scale with SMP? For example, all else being equal, will a pair of 2ghz Xeons beat out a single 3ghz? Are there certain situations (things like mail volume per active user) where SMP does well or does poorly?

Staying with the processor end of things, will Zimbra scale well out over 4 cores? Also, does Zimbra favor a particular architecture over another (K8 vs P4 vs Core)?

I've seen developers mention on this forum mention that RAID 10 is the ideal storage subsystem for Zimbra (many of small I/Os). Has anyone come across a particular disk subsystem benchmark who's results mirror Zimbra performance well (A particular IOmeter test perhaps) - for testing various configurations?

Finally, the Wiki mentions "Small", "Medium" and "Large" suggestions for splitting Zimbra between multiple machines. Are there any general rules of thumb (or metrics to watch) for when (users or mail volume) it makes sense to throw more hardware at a single machine, vs less hardware are two?