We have added nginx to our web servers, which acts as a reverse proxy and returns all static content instead of apache.
This lead to a huge performance increase, especially on sites with lots of static content (for example image galleries, html only websites, websites built with website builder). We have noticed reduced page loading times, sometimes even by 4 times.
We are also working on optimizing mysql service, which will reduce query execution time and will lead to performance increase on database sites.
We have just received 2 new servers in our datacenter location (We're collocating at Immedion datacenters), which will be fully built and setup for our clients during this week.
All new servers are built with newest generation intel quad core xeon processors, at least 24 Gigs of Ram, Raid-10 setup, 1GB/s direct line, Terabytes of storage and hardware DDOS protection.
Most of the time fighting with DDoS attacks is a painful manual process. You need to have anti-ddos scripts (to block bad IP's), install firewalls and setup rules, use apache mods, set connections limits per IP's and sometimes even nullroute server IP's (if nothing helps).
We have recently integrated a full proof protection against TCP / UDP DDoS attacks on our servers. Cisco® Anomaly Guard Module works as a hardware proxy on provided IP range, detecting and filtering out the bad traffic in it's multi step verification process, and allowing for the good traffic to pass through without any delays.