Basically, the HTML file contains the link to the image, hosted elsewhere on the internet. You download that small HTML page from BLF, and then your browser obeys the link and initiates a connection with the remove server and downloads the image. What you probably perceive as a speed increase is the reduction in the amount of time that it is taking for the new BLF test server to respond to your request. This production site is taking forever to respond to requests.
Normally we have more anonymous users than logged-in users, and anonymous users usually get a cached version of the page that takes very little resources to serve up. So this is pretty impressive considering that the static HTML cache is disabled.
On pic heavy threads is usually where it seems to be the slowest for me. On the new server the entire thread and pics load incredible faster. I couldn’t tell you what’s making the difference but they are a huge difference for me. Tried it again just now as the torture test is being run and its about like normal BLF.
It’s pretty slow now for me, just click on one link at a time. It’s because the Apache workers are all busy and a long waiting queue. I’m keeping those values fairly low to save RAM.