Originally Posted by John VV
unless you NEED the older centos 5.9 it would likely be better to use CentOS 6.3
centOS 5.9 is supported , and will be for many years , but it is starting to show it's age .
There are huge differences between the 5.x and 6.x family before you follow any recommendation to upgrade from one major release to the next review the release notes and verify that the changes aren't going to affect your environment.
For instance, I upgraded a redhat 5.3 server to a 6.x server and the new BIOSDEVNAMING feature completely screwed up my udev rules and my networking causing me to re-do a lot of work.