> and what sort of capabilities PostgreSQL has to scale across
> > multiple CPUs and hosts (multithreading, load balancing, etc).
> >
>
> Well, PostgreSQL can certainly take advantage of multiple CPU's,
> although there are some cases where we could do more (use multiple CPU
> on one query). You can also use a combination of tools like pgpool and
> slony to set up load balancing depending on your needs... though I
> should say that PostgreSQL has tremendous ability to scale up even
> without getting into all the buzzword friendly schemes.
>
Just to clarify, PostgreSQL uses multiple processes rather than, e.g.
multiple threads. The developers agree that multiple processes provide
more benefits (mostly in stability and robustness) than costs (more
connection startup costs). The startup costs are easily overcome by
using connection pooling.
Also, each query can only use one processor; a single query can't be
executed in parallel across many CPUs. However, several queries running
concurrently will be spread across the available CPUs.
Slony <http://slony.info> and something like pgpool
<http://www2b.biglobe.ne.jp/~caco/pgpool/index-e.html> can work together
to make a great replication system with load balancing. No one
replication solution is perfect for all, and PostgreSQL has other
options, so you should post your business's needs if you want more
specific advice.
Regards,
Jeff Davis
