A few weeks ago, I botched the upgrade of the W3 Total Cache plugin on my site. Since I had recently setup Pingdom website monitoring, I decided to leave it off for a bit and monitor the effects. The results were pretty dramatic — site response time doubled immediately to over 1,200 ms without the caching plugin activated! I turned the plugin back on yesterday, and site response time dropped back down to around 600 ms. I can’t recommend this WordPress optimization plugin enough. Check out this graph (click to enlarge).
Without Pingdom, I would have never realized the impact W3 Total Cache had on my site. Which brings me to recommendation #2: sign-up for Pingdom. If you only use 1 monitor, it’s totally free.