PG defaults and performance (was Re: Unexpectedly high disk space usage RESOLVED (Manual reindex/vacuum))

On Sat, Nov 10, 2012 at 12:26 PM, Steve Crawford
<scrawford(at)pinpointresearch(dot)com> wrote:
> Don't do that. Defaults are good for ensuring that PostgreSQL will start on
> the widest reasonable variety of systems. They are *terrible* for
> performance and are certainly wrong for the system you describe.

Tuning a PostgreSQL database is a major science, but is there a
reasonably easy way to get a stable baseline for comparison? We've
been exploring different hosting options recently, and one thing we
want to know is how well Postgres will perform. To that end, we've
been using pgbench on a default configuration Postgres, on the
expectation that that'll at least be consistent (that is, if a Cloud
Host A instance does X tps and Cloud Host B does 2*X, then we can
expect host B to deliver roughly double performance in production).
How valid is this assumption? Broadly, or totally not?

ChrisA