> With regards to other jobs on the server, there is a MySQL server on it
> as well, which from time to time has some multi-second queries generated
> from a webserver also on this host, but the MySQL is running with nice
> 10 (PostgreSQL isn't nice'd).
Do those MySQL queries hit disk hard?
I've never seen PostgreSQL have hicups like you describe when running on
a machine by itself. I have experienced similar issues when another
process (cron job in my case) caused brief swapping to occur.