Re:

I was gonna tell you to turn off full page writes, but in 8.1 that
setting is ignored.  For reference, here's the pages that you should
look at for this:

http://www.postgresql.org/docs/8.1/static/runtime-config-wal.html
http://www.postgresql.org/docs/8.1/static/wal-configuration.html

For 9.1, the same pages:

http://www.postgresql.org/docs/9.1/static/runtime-config-wal.html
http://www.postgresql.org/docs/9.1/static/wal-configuration.html

For future reference, if you want to learn more about performance
tuning postgresql, Performance PostgreSQL by Greg Smith is THE book to
have.