How do you update a driver after a fresh CentOS installation?

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http://www.linuxquestions.org – I've been a long time Debian user but now I'm working with Red Hat and I'm a bit lost. I just installed a fresh install of CentOS 5.5 on a new Dell server. Dell provides a current Red Hat 5.5 driver for mpt2sas. How do I install this driver? The Dell instructions are not that helpful. They explain an RPM Install and a DKMS Install - what's the difference between the two? Thanks in advance. (HowTos)