http://www.mysqlperformanceblog.com/2011/04/04/innodb-flushing-theory-and-solutions/ blog posts that describes how MySQL InnoDB flushes data to disk (also see bgwriter, checkpoint_* parameters in PostgreSQL)
http://lwn.net/Articles/418918/#Comments Interesting discussion on LWN about an article describes problem with packet loss on home broadband networks due to improper buffer sizes in various network gear (routers, cable/dsl modems, switches, etc) along the route path.
http://www.westnet.com/~gsmith/content/postgresql/chkp-bgw-83.htm improvements to PostgreSQL that could be made by tuning wal/background writer processes