The main advantage of using Red Hat Enterprise Linux over something more cutting-edge like Fedora is the length of time Red Hat supports their Enterprise product.
The Fedora Project only supports the current and previous versions of Fedora (formerly Fedora Core). Since Fedora utilizes a six month release cycle, you can only expect official support for a particular version of Fedora for about a year. (Please note that there is nothing wrong with this model. Fedora was not conceived as a production operating system to replace RHEL.)
So, if you choose Red Hat Enterprise Linux how long can you expect the product to be supported by Red Hat?
Seven years should be long enough for you to migrate that old server to the next version of the operating system, don't you think?
It's important to note that Red Hat will only support hardware-related updates through the first three years. After 3.5 years, Red Hat will only provide security updates and major bugfixes. This means that you have 3.5 years to determine if the platform is going to work for you before it's set in stone. After that, you can at least rest easy knowing that you have another 3.5 years of security updates before you are truly forced to upgrade.
As a matter of convenience, I've included the end of support dates for the current versions of Red Hat Enterprise Linux in the table below.
Version End of Support Date
- RHEL 2.1 May 31, 2009
- RHEL 3 Oct 31, 2010
- RHEL 4 Feb 29, 2012
- RHEL 5 Mar 31, 2014
Table 1. RHEL End of Support Dates