Down, Not Across

http://www.thegeekstuff.com/2011/03/sar-examples/

http://linuxhostingsupport.net/blog/tag/list-high-cpu-usage-processes

http://stackoverflow.com/questions/7325211/tuning-nginx-worker-process-to-obtain-100k-hits-per-min

http://blog.martinfjordvald.com/2011/04/optimizing-nginx-for-high-traffic-loads/

Haven't read it yet, but I plan to...

http://bhavin.directi.com/iostat-and-disk-utilization-monitoring-nirvana/

http://blog.serverfault.com/2010/07/06/777852755/

http://www.pythian.com/blog/basic-io-monitoring-on-linux/

http://sys-log.bencane.com/2012/08/troubleshooting-high-io-wait-in-linux/