Yesterday the site was moved to a new server! Now we have 2GB of RAM (was 1GB), 8 core E5-2650L Xeon @1.8GHz 20MB cache CPU (was 4 core L5520 Xeon @ 2.27GHz 8MB cache), 48 GB or storage space (was 40GB), 4TB(!!!!) of monthly transfer (was 400GB), 10Gb/s Ethernet infrastructure (was 1Gb/s), new disks with more cache.
Not bad, huh? The most important upgrade is the RAM. One extra Gigabyte allows more possible connections and more cache (APC, pagespeed, MySQL). Not much, actually, you may not even notice the improvements (I think the latency decreased by 10-15%), but now we have more breathing space, more overload protection, more stability and almost unlimited bandwidth.
For example, as long as nobody’s ripping the whole site (I immediately block such IP addresses), the PHP content is served entirely from the APC cache (100% hit rate)!