The task then becomes one of ensuring that your distribution of choice is supported by at least a Tier 2, if not a Tier 1, hardware vendor. This would guarantee support for vendor-specific system hardware, such as RAID arrays, and can be a boon when troubleshooting problems. This criteria will knock your list down to a manageable three or four distributions. Red Hat is by far the most widely supported distribution in terms of Tier 1 hardware vendors, but many others, including SuSE, Debian and even Slackware, are supported by companies such as Hewlett-Packard Co.
If you're planning to use your GNU/Linux server as a file/print server, you'll want to check each candidate distribution on its level of support for your printer(s). While most distributions support a large array of printers, some older models that were targeted to Windows OSs are GDI (Graphics Device Interface)-based, and support for such printers on GNU/Linux is difficult to find. This is true of other peripherals including scanners and plotters. A corporate-class distribution should have a list of devices supported or be able to point to the specific applications supporting these devices, and you should check them before making a final decision.
Once you've found a distribution that's suitable for your hardware platform, you'll want to start digging into software support. Depending on what functions your GNU/Linux server will be performing, you'll need to compile a list of necessary software and determine whether applications included in the distribution will suffice or if you'll need to find a third-party solution.
If you're using your GNU/Linux server for file serving/sharing, you'll want to back it up, right? Unfortunately, the utilities included in most distributions aren't corporate-class and would be difficult to fit into existing enterprise-management systems. Luckily, companies like Veritas Software have been supporting GNU/Linux for several years and offer the same support as provided to other OS-based servers.