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

On Fri, Nov 9, 2012 at 6:17 PM, Chris Angelico <rosuav(at)gmail(dot)com> wrote:
> 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?

Totally not. With default settings and default pgbench, the easiest
way for host B to beat host A is by lying about the durability of
fsync.

Cheers,

Jeff