Site UptimeI have significantly improved our site performance in the last month. I did all the site optimization steps by the book, found a lot of new things and fine-tuned existing ideas. There are a couple of good ideas I am yet to implement like using Lighttpd server instead of Apache 2.

Site Response TimeI am writing a detailed article on all the site optimization steps we have taken, what worked and what didn't and why. You would be surprised with the results. It should be ready in 2-3 weeks after I complete this phase of optimizations with master-master replication of MySQL databases & Lighttpd.I have a server in-waiting which we will soon use to replicate our sites.

In the end the ability to measure the improvements and persistence paid off. As you had read so far into the article I will offer two hints:
1. Watch your MySQL. It is most likely where the bottleneck is, specially for WordPress sites.
2. Use ajaxMyTop to watch MySQL during heavy load period. You can also use the MySQL's slow query log, but I found using mtop to be the best idea.