[defen]

Postgres's default settings are pretty bad. You'll want to increase shared_buffers to somewhere between 25%-40% of your available system RAM (if you're using 9.2 or earlier, you'll probably need to update SHMMAX using sysctl) instead of the default 128MB.

For the thing you described, you probably also want synchronous_commit=off. That means you might lose some commits in the case of a crash, but you won't get data corruption from it, and writes will be much faster.