I would say caching, on multiple levels (CPU, DB, File System). By
splitting at least some of the load, it's possible for parts of the
cache to become old and get flushed. When everything is on one
machine, the box has a complete picture of the traffic patterns and
can optimize better.
A puzzler for you guys.. all plausible explanations (and suggestions
for proving them) gratefully received.
We run several MySQL database servers in the traditional master-slave
configuration and attempt (rather poorly) to spread select queries
between them. Normally the slave gets 1/3 o
