We have a number of servers, all in the same datacenter, all similar spec, all run the same application (LAMP ecommerce app), all have similar traffic levels and all have similar average load. However, one of these servers regularly scores much worse than all the other servers in response time reports from Pingdom. All our servers bar this one have response time averages between 190ms - 210ms however one server avaerages between 280ms - 300ms. One of the only differences between these servers is the version of CentOS. On the slower site the version is 4.8 but on the faster servers they are all running 5.5. Is it likely that the OS version is enough to slow down response time on the server or is it likely to be something else?