"Ed L." <pgsql@bluepolka.net> writes:
> Then what scenarios, if any, merit theory (2) over theory (1)?
I'd only consider a large-cache setting on a machine that's dedicated to
running the database (where "dedicated" means "that's the only thing you
care about performance of", as in your first scenario). Even then I'd
test it against the other way. As Andrew Sullivan notes nearby, our
experience has been that the PostgreSQL buffer manager isn't all that
efficient about managing large caches. It's possible that Jan's current
work will change that situation in 7.5, but I'd still test first ...
regards, tom lane