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://vbtechsupport.com/606/ Sysbench-based benchmark comparing OLTP workloads for different builds and forks of MySQL on 64-core intel machine (Quad Intel Xeon L7555 ) . Only one definitive result is that MySQL cannot scale beyond 8 or 16 cores, or in some cases beyond just 2 cores (booo! ). In all cases performance went down when more than 24 cores were used .